diff --git a/docs/conf.py b/docs/conf.py
index c64063f6..e04e1750 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -18,7 +18,7 @@
 # https://www.sphinx-doc.org/en/master/usage/configuration.html#project-information
 
 project = "adam"
-copyright = "2021, Artificial and Mechanical Intelligence Lab"
+copyright = "Artificial and Mechanical Intelligence Lab"
 author = "Artificial and Mechanical Intelligence Lab"
 # get release from git tag
 
diff --git a/setup.py b/setup.py
index b9394a34..d7b82f52 100644
--- a/setup.py
+++ b/setup.py
@@ -1,6 +1,5 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 # This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
 
 from setuptools import setup
 
diff --git a/src/adam/__init__.py b/src/adam/__init__.py
index 6d51bece..3fb0daba 100644
--- a/src/adam/__init__.py
+++ b/src/adam/__init__.py
@@ -1,5 +1,3 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 from adam.core import Representations
diff --git a/src/adam/casadi/__init__.py b/src/adam/casadi/__init__.py
index 1c3b0795..583c07a7 100644
--- a/src/adam/casadi/__init__.py
+++ b/src/adam/casadi/__init__.py
@@ -1,6 +1,4 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 from .casadi_like import CasadiLike
 from .computations import KinDynComputations
diff --git a/src/adam/casadi/casadi_like.py b/src/adam/casadi/casadi_like.py
index b8a5be41..9feac024 100644
--- a/src/adam/casadi/casadi_like.py
+++ b/src/adam/casadi/casadi_like.py
@@ -1,6 +1,4 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 from dataclasses import dataclass
 from typing import Union
diff --git a/src/adam/casadi/computations.py b/src/adam/casadi/computations.py
index 8b0dc66d..ff67fda2 100644
--- a/src/adam/casadi/computations.py
+++ b/src/adam/casadi/computations.py
@@ -1,10 +1,7 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 import casadi as cs
 import numpy as np
-from typing import Union
 
 from adam.casadi.casadi_like import SpatialMath
 from adam.core import RBDAlgorithms
@@ -13,15 +10,13 @@
 
 
 class KinDynComputations:
-    """This is a small class that retrieves robot quantities represented in a symbolic fashion using CasADi
-    in mixed representation, for Floating Base systems - as humanoid robots.
-    """
+    """Class that retrieves robot quantities using CasADi for Floating Base systems."""
 
     def __init__(
         self,
         urdfstring: str,
         joints_name_list: list = None,
-        root_link: str = "root_link",
+        root_link: str = None,
         gravity: np.array = np.array([0.0, 0.0, -9.80665, 0.0, 0.0, 0.0]),
         f_opts: dict = dict(jit=False, jit_options=dict(flags="-Ofast"), cse=True),
     ) -> None:
@@ -29,7 +24,7 @@ def __init__(
         Args:
             urdfstring (str): either path or string of the urdf
             joints_name_list (list): list of the actuated joints
-            root_link (str, optional): the first link. Defaults to 'root_link'.
+            root_link (str, optional): Deprecated. The root link is automatically chosen as the link with no parent in the URDF. Defaults to None.
         """
         math = SpatialMath()
         factory = URDFModelFactory(path=urdfstring, math=math)
@@ -38,6 +33,10 @@ def __init__(
         self.NDoF = self.rbdalgos.NDoF
         self.g = gravity
         self.f_opts = f_opts
+        if root_link is not None:
+            raise DeprecationWarning(
+                "The root_link argument is not used. The root link is automatically chosen as the link with no parent in the URDF"
+            )
 
     def set_frame_velocity_representation(
         self, representation: Representations
@@ -57,7 +56,7 @@ def mass_matrix_fun(self) -> cs.Function:
         """
         base_transform = cs.SX.sym("H", 4, 4)
         joint_positions = cs.SX.sym("s", self.NDoF)
-        [M, _] = self.rbdalgos.crba(base_transform, joint_positions)
+        M, _ = self.rbdalgos.crba(base_transform, joint_positions)
         return cs.Function(
             "M", [base_transform, joint_positions], [M.array], self.f_opts
         )
@@ -70,7 +69,7 @@ def centroidal_momentum_matrix_fun(self) -> cs.Function:
         """
         base_transform = cs.SX.sym("H", 4, 4)
         joint_positions = cs.SX.sym("s", self.NDoF)
-        [_, Jcm] = self.rbdalgos.crba(base_transform, joint_positions)
+        _, Jcm = self.rbdalgos.crba(base_transform, joint_positions)
         return cs.Function(
             "Jcm", [base_transform, joint_positions], [Jcm.array], self.f_opts
         )
@@ -228,55 +227,51 @@ def get_total_mass(self) -> float:
         """
         return self.rbdalgos.get_total_mass()
 
-    def mass_matrix(
-        self, base_transform: Union[cs.SX, cs.DM], joint_positions: Union[cs.SX, cs.DM]
-    ):
+    def mass_matrix(self, base_transform: cs.SX, joint_positions: cs.SX):
         """Returns the Mass Matrix functions computed the CRBA
 
         Args:
-            base_transform (Union[cs.SX, cs.DM]): The homogenous transform from base to world frame
-            joint_positions (Union[cs.SX, cs.DM]): The joints position
+            base_transform (cs.SX): The homogenous transform from base to world frame
+            joint_positions (cs.SX): The joints position
 
         Returns:
-            M (Union[cs.SX, cs.DM]): Mass Matrix
+            M (cs.SX): Mass Matrix
         """
         if isinstance(base_transform, cs.MX) and isinstance(joint_positions, cs.MX):
             raise ValueError(
                 "You are using casadi MX. Please use the function KinDynComputations.mass_matrix_fun()"
             )
 
-        [M, _] = self.rbdalgos.crba(base_transform, joint_positions)
+        M, _ = self.rbdalgos.crba(base_transform, joint_positions)
         return M.array
 
-    def centroidal_momentum_matrix(
-        self, base_transform: Union[cs.SX, cs.DM], joint_positions: Union[cs.SX, cs.DM]
-    ):
+    def centroidal_momentum_matrix(self, base_transform: cs.SX, joint_positions: cs.SX):
         """Returns the Centroidal Momentum Matrix functions computed the CRBA
 
         Args:
-            base_transform (Union[cs.SX, cs.DM]): The homogenous transform from base to world frame
-            joint_positions (Union[cs.SX, cs.DM]): The joints position
+            base_transform (cs.SX): The homogenous transform from base to world frame
+            joint_positions (cs.SX): The joints position
 
         Returns:
-            Jcc (Union[cs.SX, cs.DM]): Centroidal Momentum matrix
+            Jcc (cs.SX): Centroidal Momentum matrix
         """
         if isinstance(base_transform, cs.MX) and isinstance(joint_positions, cs.MX):
             raise ValueError(
                 "You are using casadi MX. Please use the function KinDynComputations.centroidal_momentum_matrix_fun()"
             )
 
-        [_, Jcm] = self.rbdalgos.crba(base_transform, joint_positions)
+        _, Jcm = self.rbdalgos.crba(base_transform, joint_positions)
         return Jcm.array
 
-    def relative_jacobian(self, frame: str, joint_positions: Union[cs.SX, cs.DM]):
+    def relative_jacobian(self, frame: str, joint_positions: cs.SX):
         """Returns the Jacobian between the root link and a specified frame frames
 
         Args:
             frame (str): The tip of the chain
-            joint_positions (Union[cs.SX, cs.DM]): The joints position
+            joint_positions (cs.SX): The joints position
 
         Returns:
-            J (Union[cs.SX, cs.DM]): The Jacobian between the root and the frame
+            J (cs.SX): The Jacobian between the root and the frame
         """
         if isinstance(joint_positions, cs.MX):
             raise ValueError(
@@ -288,22 +283,22 @@ def relative_jacobian(self, frame: str, joint_positions: Union[cs.SX, cs.DM]):
     def jacobian_dot(
         self,
         frame: str,
-        base_transform: Union[cs.SX, cs.DM],
-        joint_positions: Union[cs.SX, cs.DM],
-        base_velocity: Union[cs.SX, cs.DM],
-        joint_velocities: Union[cs.SX, cs.DM],
-    ) -> Union[cs.SX, cs.DM]:
+        base_transform: cs.SX,
+        joint_positions: cs.SX,
+        base_velocity: cs.SX,
+        joint_velocities: cs.SX,
+    ) -> cs.SX:
         """Returns the Jacobian derivative relative to the specified frame
 
         Args:
             frame (str): The frame to which the jacobian will be computed
-            base_transform (Union[cs.SX, cs.DM]): The homogenous transform from base to world frame
-            joint_positions (Union[cs.SX, cs.DM]): The joints position
-            base_velocity (Union[cs.SX, cs.DM]): The base velocity in mixed representation
-            joint_velocities (Union[cs.SX, cs.DM]): The joint velocities
+            base_transform (cs.SX): The homogenous transform from base to world frame
+            joint_positions (cs.SX): The joints position
+            base_velocity (cs.SX): The base velocity in mixed representation
+            joint_velocities (cs.SX): The joint velocities
 
         Returns:
-            Jdot (Union[cs.SX, cs.DM]): The Jacobian derivative relative to the frame
+            Jdot (cs.SX): The Jacobian derivative relative to the frame
         """
         if (
             isinstance(base_transform, cs.MX)
@@ -321,18 +316,18 @@ def jacobian_dot(
     def forward_kinematics(
         self,
         frame: str,
-        base_transform: Union[cs.SX, cs.DM],
-        joint_positions: Union[cs.SX, cs.DM],
+        base_transform: cs.SX,
+        joint_positions: cs.SX,
     ):
         """Computes the forward kinematics relative to the specified frame
 
         Args:
             frame (str): The frame to which the fk will be computed
-            base_transform (Union[cs.SX, cs.DM]): The homogenous transform from base to world frame
-            joint_positions (Union[cs.SX, cs.DM]): The joints position
+            base_transform (cs.SX): The homogenous transform from base to world frame
+            joint_positions (cs.SX): The joints position
 
         Returns:
-            H (Union[cs.SX, cs.DM]): The fk represented as Homogenous transformation matrix
+            H (cs.SX): The fk represented as Homogenous transformation matrix
         """
         if isinstance(base_transform, cs.MX) and isinstance(joint_positions, cs.MX):
             raise ValueError(
@@ -347,12 +342,12 @@ def jacobian(self, frame: str, base_transform, joint_positions):
         """Returns the Jacobian relative to the specified frame
 
         Args:
-            base_transform (Union[cs.SX, cs.DM]): The homogenous transform from base to world frame
-            s (Union[cs.SX, cs.DM]): The joints position
+            base_transform (cs.SX): The homogenous transform from base to world frame
+            s (cs.SX): The joints position
             frame (str): The frame to which the jacobian will be computed
 
         Returns:
-            J_tot (Union[cs.SX, cs.DM]): The Jacobian relative to the frame
+            J_tot (cs.SX): The Jacobian relative to the frame
         """
         if isinstance(base_transform, cs.MX) and isinstance(joint_positions, cs.MX):
             raise ValueError(
@@ -363,22 +358,22 @@ def jacobian(self, frame: str, base_transform, joint_positions):
 
     def bias_force(
         self,
-        base_transform: Union[cs.SX, cs.DM],
-        joint_positions: Union[cs.SX, cs.DM],
-        base_velocity: Union[cs.SX, cs.DM],
-        joint_velocities: Union[cs.SX, cs.DM],
-    ) -> Union[cs.SX, cs.DM]:
+        base_transform: cs.SX,
+        joint_positions: cs.SX,
+        base_velocity: cs.SX,
+        joint_velocities: cs.SX,
+    ) -> cs.SX:
         """Returns the bias force of the floating-base dynamics equation,
         using a reduced RNEA (no acceleration and external forces)
 
         Args:
-            base_transform (Union[cs.SX, cs.DM]): The homogenous transform from base to world frame
-            joint_positions (Union[cs.SX, cs.DM]): The joints position
-            base_velocity (Union[cs.SX, cs.DM]): The base velocity in mixed representation
-            joint_velocities (Union[cs.SX, cs.DM]): The joints velocity
+            base_transform (cs.SX): The homogenous transform from base to world frame
+            joint_positions (cs.SX): The joints position
+            base_velocity (cs.SX): The base velocity in mixed representation
+            joint_velocities (cs.SX): The joints velocity
 
         Returns:
-            h (Union[cs.SX, cs.DM]): the bias force
+            h (cs.SX): the bias force
         """
         if (
             isinstance(base_transform, cs.MX)
@@ -396,22 +391,22 @@ def bias_force(
 
     def coriolis_term(
         self,
-        base_transform: Union[cs.SX, cs.DM],
-        joint_positions: Union[cs.SX, cs.DM],
-        base_velocity: Union[cs.SX, cs.DM],
-        joint_velocities: Union[cs.SX, cs.DM],
-    ) -> Union[cs.SX, cs.DM]:
+        base_transform: cs.SX,
+        joint_positions: cs.SX,
+        base_velocity: cs.SX,
+        joint_velocities: cs.SX,
+    ) -> cs.SX:
         """Returns the coriolis term of the floating-base dynamics equation,
         using a reduced RNEA (no acceleration and external forces)
 
         Args:
-            base_transform (Union[cs.SX, cs.DM]): The homogenous transform from base to world frame
-            joint_positions (Union[cs.SX, cs.DM]): The joints position
-            base_velocity (Union[cs.SX, cs.DM]): The base velocity in mixed representation
-            joint_velocities (Union[cs.SX, cs.DM]): The joints velocity
+            base_transform (cs.SX): The homogenous transform from base to world frame
+            joint_positions (cs.SX): The joints position
+            base_velocity (cs.SX): The base velocity in mixed representation
+            joint_velocities (cs.SX): The joints velocity
 
         Returns:
-            C (Union[cs.SX, cs.DM]): the Coriolis term
+            C (cs.SX): the Coriolis term
         """
         if (
             isinstance(base_transform, cs.MX)
@@ -431,18 +426,16 @@ def coriolis_term(
             np.zeros(6),
         ).array
 
-    def gravity_term(
-        self, base_transform: Union[cs.SX, cs.DM], joint_positions: Union[cs.SX, cs.DM]
-    ) -> Union[cs.SX, cs.DM]:
+    def gravity_term(self, base_transform: cs.SX, joint_positions: cs.SX) -> cs.SX:
         """Returns the gravity term of the floating-base dynamics equation,
         using a reduced RNEA (no acceleration and external forces)
 
         Args:
-            base_transform (Union[cs.SX, cs.DM]): The homogenous transform from base to world frame
-            joint_positions (Union[cs.SX, cs.DM]): The joints position
+            base_transform (cs.SX): The homogenous transform from base to world frame
+            joint_positions (cs.SX): The joints position
 
         Returns:
-            G (Union[cs.SX, cs.DM]): the gravity term
+            G (cs.SX): the gravity term
         """
         if isinstance(base_transform, cs.MX) and isinstance(joint_positions, cs.MX):
             raise ValueError(
@@ -457,17 +450,15 @@ def gravity_term(
             self.g,
         ).array
 
-    def CoM_position(
-        self, base_transform: Union[cs.SX, cs.DM], joint_positions: Union[cs.SX, cs.DM]
-    ) -> Union[cs.SX, cs.DM]:
+    def CoM_position(self, base_transform: cs.SX, joint_positions: cs.SX) -> cs.SX:
         """Returns the CoM positon
 
         Args:
-            base_transform (Union[cs.SX, cs.DM]): The homogenous transform from base to world frame
-            joint_positions (Union[cs.SX, cs.DM]): The joints position
+            base_transform (cs.SX): The homogenous transform from base to world frame
+            joint_positions (cs.SX): The joints position
 
         Returns:
-            CoM (Union[cs.SX, cs.DM]): The CoM position
+            CoM (cs.SX): The CoM position
         """
         if isinstance(base_transform, cs.MX) and isinstance(joint_positions, cs.MX):
             raise ValueError(
diff --git a/src/adam/core/__init__.py b/src/adam/core/__init__.py
index b8a1addc..18b8d98c 100644
--- a/src/adam/core/__init__.py
+++ b/src/adam/core/__init__.py
@@ -1,6 +1,4 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 from .constants import Representations
 from .rbd_algorithms import RBDAlgorithms
diff --git a/src/adam/core/rbd_algorithms.py b/src/adam/core/rbd_algorithms.py
index b364daaf..4c67d980 100644
--- a/src/adam/core/rbd_algorithms.py
+++ b/src/adam/core/rbd_algorithms.py
@@ -1,6 +1,5 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 import numpy.typing as npt
 
 from adam.core.constants import Representations
diff --git a/src/adam/jax/__init__.py b/src/adam/jax/__init__.py
index 70be81d8..87ca661e 100644
--- a/src/adam/jax/__init__.py
+++ b/src/adam/jax/__init__.py
@@ -1,6 +1,5 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
 from .computations import KinDynComputations
 from .jax_like import JaxLike
diff --git a/src/adam/jax/computations.py b/src/adam/jax/computations.py
index 25ad6adc..82d3611f 100644
--- a/src/adam/jax/computations.py
+++ b/src/adam/jax/computations.py
@@ -1,6 +1,4 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 import jax.numpy as jnp
 import numpy as np
@@ -18,14 +16,14 @@ def __init__(
         self,
         urdfstring: str,
         joints_name_list: list = None,
-        root_link: str = "root_link",
+        root_link: str = None,
         gravity: np.array = jnp.array([0, 0, -9.80665, 0, 0, 0]),
     ) -> None:
         """
         Args:
             urdfstring (str): either path or string of the urdf
             joints_name_list (list): list of the actuated joints
-            root_link (str, optional): the first link. Defaults to 'root_link'.
+            root_link (str, optional): Deprecated. The root link is automatically chosen as the link with no parent in the URDF. Defaults to None.
         """
         math = SpatialMath()
         factory = URDFModelFactory(path=urdfstring, math=math)
@@ -33,6 +31,10 @@ def __init__(
         self.rbdalgos = RBDAlgorithms(model=model, math=math)
         self.NDoF = self.rbdalgos.NDoF
         self.g = gravity
+        if root_link is not None:
+            raise DeprecationWarning(
+                "The root_link argument is not used. The root link is automatically chosen as the link with no parent in the URDF"
+            )
 
     def set_frame_velocity_representation(
         self, representation: Representations
diff --git a/src/adam/jax/jax_like.py b/src/adam/jax/jax_like.py
index 23ddc2a1..849968ce 100644
--- a/src/adam/jax/jax_like.py
+++ b/src/adam/jax/jax_like.py
@@ -1,6 +1,5 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
 from dataclasses import dataclass
 from typing import Union
diff --git a/src/adam/model/__init__.py b/src/adam/model/__init__.py
index 0426e317..3c23a54a 100644
--- a/src/adam/model/__init__.py
+++ b/src/adam/model/__init__.py
@@ -1,4 +1,4 @@
-from .abc_factories import Joint, Link, ModelFactory, Inertial, Pose
+from .abc_factories import Inertial, Joint, Link, ModelFactory, Pose
 from .model import Model
 from .std_factories.std_joint import StdJoint
 from .std_factories.std_link import StdLink
diff --git a/src/adam/model/abc_factories.py b/src/adam/model/abc_factories.py
index 4720588f..576ad665 100644
--- a/src/adam/model/abc_factories.py
+++ b/src/adam/model/abc_factories.py
@@ -1,6 +1,5 @@
 import abc
 import dataclasses
-from typing import List
 
 import numpy.typing as npt
 
@@ -11,8 +10,8 @@
 class Pose:
     """Pose class"""
 
-    xyz: List
-    rpy: List
+    xyz: list
+    rpy: list
 
 
 @dataclasses.dataclass
@@ -46,7 +45,7 @@ class Joint(abc.ABC):
     parent: str
     child: str
     type: str
-    axis: List
+    axis: list
     origin: Pose
     limit: Limits
     idx: int
@@ -126,9 +125,9 @@ class Link(abc.ABC):
 
     math: SpatialMath
     name: str
-    visuals: List
+    visuals: list
     inertial: Inertial
-    collisions: List
+    collisions: list
 
     @abc.abstractmethod
     def spatial_inertia(self) -> npt.ArrayLike:
@@ -178,25 +177,25 @@ def build_joint(self) -> Joint:
         pass
 
     @abc.abstractmethod
-    def get_links(self) -> List[Link]:
+    def get_links(self) -> list[Link]:
         """
         Returns:
-            List[Link]: the list of the link
+            list[Link]: the list of the link
         """
         pass
 
     @abc.abstractmethod
-    def get_frames(self) -> List[Link]:
+    def get_frames(self) -> list[Link]:
         """
         Returns:
-            List[Link]: the list of the frames
+            list[Link]: the list of the frames
         """
         pass
 
     @abc.abstractmethod
-    def get_joints(self) -> List[Joint]:
+    def get_joints(self) -> list[Joint]:
         """
         Returns:
-            List[Joint]: the list of the joints
+            list[Joint]: the list of the joints
         """
         pass
diff --git a/src/adam/model/conversions/idyntree.py b/src/adam/model/conversions/idyntree.py
index bbd8fd8e..e4a30892 100644
--- a/src/adam/model/conversions/idyntree.py
+++ b/src/adam/model/conversions/idyntree.py
@@ -1,11 +1,9 @@
 import idyntree.bindings
 import numpy as np
 import urdf_parser_py.urdf
-from typing import List
-
 
+from adam.model.abc_factories import Joint, Link
 from adam.model.model import Model
-from adam.model.abc_factories import Link, Joint
 
 
 def to_idyntree_solid_shape(
@@ -63,7 +61,7 @@ def to_idyntree_solid_shape(
 
 def to_idyntree_link(
     link: Link,
-) -> [idyntree.bindings.Link, List[idyntree.bindings.SolidShape]]:
+) -> tuple[idyntree.bindings.Link, list[idyntree.bindings.SolidShape]]:
     """
     Args:
         link (Link): the link to convert
diff --git a/src/adam/model/model.py b/src/adam/model/model.py
index 887b4e7a..1696edcb 100644
--- a/src/adam/model/model.py
+++ b/src/adam/model/model.py
@@ -1,5 +1,4 @@
 import dataclasses
-from typing import Dict, List
 
 from adam.model.abc_factories import Joint, Link, ModelFactory
 from adam.model.tree import Tree
@@ -11,24 +10,29 @@ class Model:
     Model class. It describes the robot using links and frames and their connectivity"""
 
     name: str
-    links: Dict[str, Link]
-    frames: Dict[str, Link]
-    joints: Dict[str, Joint]
+    links: dict[str, Link]
+    frames: dict[str, Link]
+    joints: dict[str, Joint]
     tree: Tree
     NDoF: int
-    actuated_joints: List[str]
+    actuated_joints: list[str]
 
-    def __post_init__(self):
-        """set the "length of the model as the number of links"""
-        self.N = len(self.links)
+    @property
+    def N(self) -> int:
+        """
+
+        Returns:
+            int: the number of links in the model
+        """
+        return len(self.links)
 
     @staticmethod
-    def build(factory: ModelFactory, joints_name_list: List[str] = None) -> "Model":
+    def build(factory: ModelFactory, joints_name_list: list[str] = None) -> "Model":
         """generates the model starting from the list of joints and the links-joints factory
 
         Args:
             factory (ModelFactory): the factory that generates the links and the joints, starting from a description (eg. urdf)
-            joints_name_list (List[str]): the list of the actuated joints
+            joints_name_list (list[str]): the list of the actuated joints
 
         Returns:
             Model: the model describing the robot
@@ -63,9 +67,9 @@ def build(factory: ModelFactory, joints_name_list: List[str] = None) -> "Model":
         tree = Tree.build_tree(links=links_list, joints=joints_list)
 
         # generate some useful dict
-        joints: Dict[str, Joint] = {joint.name: joint for joint in joints_list}
-        links: Dict[str, Link] = {link.name: link for link in links_list}
-        frames: Dict[str, Link] = {frame.name: frame for frame in frames_list}
+        joints: dict[str, Joint] = {joint.name: joint for joint in joints_list}
+        links: dict[str, Link] = {link.name: link for link in links_list}
+        frames: dict[str, Link] = {frame.name: frame for frame in frames_list}
 
         return Model(
             name=factory.name,
@@ -77,7 +81,7 @@ def build(factory: ModelFactory, joints_name_list: List[str] = None) -> "Model":
             actuated_joints=joints_name_list,
         )
 
-    def get_joints_chain(self, root: str, target: str) -> List[Joint]:
+    def get_joints_chain(self, root: str, target: str) -> list[Joint]:
         """generate the joints chains from a link to a link
 
         Args:
@@ -85,7 +89,7 @@ def get_joints_chain(self, root: str, target: str) -> List[Joint]:
             target (str): the target link
 
         Returns:
-            List[Joint]: the list of the joints
+            list[Joint]: the list of the joints
         """
 
         if target not in list(self.links) and target not in list(self.frames):
diff --git a/src/adam/model/std_factories/std_link.py b/src/adam/model/std_factories/std_link.py
index 7754747d..49475d73 100644
--- a/src/adam/model/std_factories/std_link.py
+++ b/src/adam/model/std_factories/std_link.py
@@ -2,7 +2,7 @@
 import urdf_parser_py.urdf
 
 from adam.core.spatial_math import SpatialMath
-from adam.model import Link, Inertial, Pose
+from adam.model import Inertial, Link, Pose
 
 
 class StdLink(Link):
diff --git a/src/adam/model/std_factories/std_model.py b/src/adam/model/std_factories/std_model.py
index 9f3a1dcd..68337bdf 100644
--- a/src/adam/model/std_factories/std_model.py
+++ b/src/adam/model/std_factories/std_model.py
@@ -1,7 +1,7 @@
+import os
 import pathlib
-from typing import List
 import xml.etree.ElementTree as ET
-import os
+
 import urdf_parser_py.urdf
 
 from adam.core.spatial_math import SpatialMath
@@ -85,17 +85,17 @@ def __init__(self, path: str, math: SpatialMath):
         )
         self.name = self.urdf_desc.name
 
-    def get_joints(self) -> List[StdJoint]:
+    def get_joints(self) -> list[StdJoint]:
         """
         Returns:
-            List[StdJoint]: build the list of the joints
+            list[StdJoint]: build the list of the joints
         """
         return [self.build_joint(j) for j in self.urdf_desc.joints]
 
-    def get_links(self) -> List[StdLink]:
+    def get_links(self) -> list[StdLink]:
         """
         Returns:
-            List[StdLink]: build the list of the links
+            list[StdLink]: build the list of the links
 
         A link is considered a "real" link if
         - it has an inertial
@@ -116,10 +116,10 @@ def get_links(self) -> List[StdLink]:
             )
         ]
 
-    def get_frames(self) -> List[StdLink]:
+    def get_frames(self) -> list[StdLink]:
         """
         Returns:
-            List[StdLink]: build the list of the links
+            list[StdLink]: build the list of the links
 
         A link is considered a "fake" link (frame) if
         - it has no inertial
diff --git a/src/adam/model/tree.py b/src/adam/model/tree.py
index 73d36210..e0361e21 100644
--- a/src/adam/model/tree.py
+++ b/src/adam/model/tree.py
@@ -1,5 +1,5 @@
 import dataclasses
-from typing import Dict, Iterable, List, Tuple, Union
+from typing import Iterable, Iterator, Union
 
 from adam.model.abc_factories import Joint, Link
 
@@ -10,19 +10,19 @@ class Node:
 
     name: str
     link: Link
-    arcs: List[Joint]
-    children: List["Node"]
+    arcs: list[Joint]
+    children: list["Node"]
     parent: Union[Link, None] = None
     parent_arc: Union[Joint, None] = None
 
     def __hash__(self) -> int:
         return hash(self.name)
 
-    def get_elements(self) -> Tuple[Link, Joint, Link]:
+    def get_elements(self) -> tuple[Link, Joint, Link]:
         """returns the node with its parent arc and parent link
 
         Returns:
-            Tuple[Link, Joint, Link]: the node, the parent_arc, the parent_link
+            tuple[Link, Joint, Link]: the node, the parent_arc, the parent_link
         """
         return self.link, self.parent_arc, self.parent
 
@@ -31,24 +31,24 @@ def get_elements(self) -> Tuple[Link, Joint, Link]:
 class Tree(Iterable):
     """The directed tree class"""
 
-    graph: Dict
+    graph: dict[str, Node]
     root: str
 
     def __post_init__(self):
         self.ordered_nodes_list = self.get_ordered_nodes_list(self.root)
 
     @staticmethod
-    def build_tree(links: List[Link], joints: List[Joint]) -> "Tree":
+    def build_tree(links: list[Link], joints: list[Joint]) -> "Tree":
         """builds the tree from the connectivity of the elements
 
         Args:
-            links (List[Link])
-            joints (List[Joint])
+            links (list[Link])
+            joints (list[Joint])
 
         Returns:
             Tree: the directed tree
         """
-        nodes: Dict[str, Node] = {
+        nodes: dict[str, Node] = {
             l.name: Node(
                 name=l.name, link=l, arcs=[], children=[], parent=None, parent_arc=None
             )
@@ -68,7 +68,9 @@ def build_tree(links: List[Link], joints: List[Joint]) -> "Tree":
 
         root_link = [l for l in nodes if nodes[l].parent is None]
         if len(root_link) != 1:
-            raise ValueError("The model has more than one root link")
+            raise ValueError(
+                f"Expected only one root, found {len(root_link)}: {root_link}"
+            )
         return Tree(nodes, root_link[0])
 
     def print(self, root):
@@ -81,25 +83,25 @@ def print(self, root):
 
         pptree.print_tree(self.graph[root])
 
-    def get_ordered_nodes_list(self, start: str) -> List[str]:
+    def get_ordered_nodes_list(self, start: str) -> list[str]:
         """get the ordered list of the nodes, given the connectivity
 
         Args:
             start (str): the start node
 
         Returns:
-            List[str]: the ordered list
+            list[str]: the ordered list
         """
         ordered_list = [start]
         self.get_children(self.graph[start], ordered_list)
         return ordered_list
 
     @classmethod
-    def get_children(cls, node: Node, list: List):
+    def get_children(cls, node: Node, list: list):
         """Recursive method that finds children of child of child
         Args:
             node (Node): the analized node
-            list (List): the list of the children that needs to be filled
+            list (list): the list of the children that needs to be filled
         """
         if node.children is not []:
             for child in node.children:
@@ -136,7 +138,7 @@ def get_node_from_name(self, name: str) -> Node:
         """
         return self.graph[name]
 
-    def __iter__(self) -> Node:
+    def __iter__(self) -> Iterator[Node]:
         """This method allows to iterate on the model
         Returns:
             Node: the node istance
@@ -146,7 +148,7 @@ def __iter__(self) -> Node:
         """
         yield from [self.graph[name] for name in self.ordered_nodes_list]
 
-    def __reversed__(self) -> Node:
+    def __reversed__(self) -> Iterator[Node]:
         """
         Returns:
             Node
diff --git a/src/adam/numpy/__init__.py b/src/adam/numpy/__init__.py
index b94c17b8..b83df7b3 100644
--- a/src/adam/numpy/__init__.py
+++ b/src/adam/numpy/__init__.py
@@ -1,6 +1,4 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 from .computations import KinDynComputations
 from .numpy_like import NumpyLike
diff --git a/src/adam/numpy/computations.py b/src/adam/numpy/computations.py
index 0b72019a..9ddd2d26 100644
--- a/src/adam/numpy/computations.py
+++ b/src/adam/numpy/computations.py
@@ -1,6 +1,5 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
 import numpy as np
 
@@ -17,14 +16,14 @@ def __init__(
         self,
         urdfstring: str,
         joints_name_list: list = None,
-        root_link: str = "root_link",
+        root_link: str = None,
         gravity: np.array = np.array([0, 0, -9.80665, 0, 0, 0]),
     ) -> None:
         """
         Args:
             urdfstring (str): either path or string of the urdf
             joints_name_list (list): list of the actuated joints
-            root_link (str, optional): the first link. Defaults to 'root_link'.
+            root_link (str, optional): Deprecated. The root link is automatically chosen as the link with no parent in the URDF. Defaults to None.
         """
         math = SpatialMath()
         factory = URDFModelFactory(path=urdfstring, math=math)
@@ -32,6 +31,10 @@ def __init__(
         self.rbdalgos = RBDAlgorithms(model=model, math=math)
         self.NDoF = model.NDoF
         self.g = gravity
+        if root_link is not None:
+            raise DeprecationWarning(
+                "The root_link argument is not used. The root link is automatically chosen as the link with no parent in the URDF"
+            )
 
     def set_frame_velocity_representation(
         self, representation: Representations
diff --git a/src/adam/numpy/numpy_like.py b/src/adam/numpy/numpy_like.py
index ddfac73a..41a83d29 100644
--- a/src/adam/numpy/numpy_like.py
+++ b/src/adam/numpy/numpy_like.py
@@ -1,6 +1,5 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
 from dataclasses import dataclass
 from typing import Union
diff --git a/src/adam/parametric/__init__.py b/src/adam/parametric/__init__.py
index 6f130a0d..9947d8db 100644
--- a/src/adam/parametric/__init__.py
+++ b/src/adam/parametric/__init__.py
@@ -1,3 +1 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
diff --git a/src/adam/parametric/casadi/__init__.py b/src/adam/parametric/casadi/__init__.py
index 46a0a0ac..228bf6a3 100644
--- a/src/adam/parametric/casadi/__init__.py
+++ b/src/adam/parametric/casadi/__init__.py
@@ -1,4 +1,3 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 from .computations_parametric import KinDynComputationsParametric
diff --git a/src/adam/parametric/casadi/computations_parametric.py b/src/adam/parametric/casadi/computations_parametric.py
index e9c2b77e..4149662d 100644
--- a/src/adam/parametric/casadi/computations_parametric.py
+++ b/src/adam/parametric/casadi/computations_parametric.py
@@ -1,7 +1,4 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
-from typing import List, Union
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 import casadi as cs
 import numpy as np
@@ -10,7 +7,7 @@
 from adam.core import RBDAlgorithms
 from adam.core.constants import Representations
 from adam.model import Model
-from adam.parametric.model import URDFParametricModelFactory, ParametricLink
+from adam.parametric.model import ParametricLink, URDFParametricModelFactory
 
 
 class KinDynComputationsParametric:
@@ -23,7 +20,7 @@ def __init__(
         urdfstring: str,
         joints_name_list: list,
         links_name_list: list,
-        root_link: str = "root_link",
+        root_link: str = None,
         gravity: np.array = np.array([0.0, 0.0, -9.80665, 0.0, 0.0, 0.0]),
         f_opts: dict = dict(jit=False, jit_options=dict(flags="-Ofast")),
     ) -> None:
@@ -32,7 +29,7 @@ def __init__(
             urdfstring (str): either path or string of the urdf
             joints_name_list (list): list of the actuated joints
             links_name_list (list): list of the parametrized links
-            root_link (str, optional): the first link. Defaults to 'root_link'.
+            root_link (str, optional): Deprecated. The root link is automatically chosen as the link with no parent in the URDF. Defaults to None.
         """
         math = SpatialMath()
         n_param_links = len(links_name_list)
@@ -51,6 +48,10 @@ def __init__(
         self.NDoF = self.rbdalgos.NDoF
         self.g = gravity
         self.f_opts = f_opts
+        if root_link is not None:
+            raise DeprecationWarning(
+                "The root_link argument is not used. The root link is automatically chosen as the link with no parent in the URDF"
+            )
 
     def set_frame_velocity_representation(
         self, representation: Representations
@@ -261,7 +262,7 @@ def get_total_mass(self) -> cs.Function:
             "m", [self.length_multiplier, self.densities], [m], self.f_opts
         )
 
-    def get_original_densities(self) -> List[float]:
+    def get_original_densities(self) -> list[float]:
         """Returns the original densities of the parametric links
 
         Returns:
diff --git a/src/adam/parametric/jax/__init__.py b/src/adam/parametric/jax/__init__.py
index 04b2fc09..ff573427 100644
--- a/src/adam/parametric/jax/__init__.py
+++ b/src/adam/parametric/jax/__init__.py
@@ -1,5 +1,4 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
 from .computations_parametric import KinDynComputationsParametric
diff --git a/src/adam/parametric/jax/computations_parametric.py b/src/adam/parametric/jax/computations_parametric.py
index 3ac9c5f2..7920006a 100644
--- a/src/adam/parametric/jax/computations_parametric.py
+++ b/src/adam/parametric/jax/computations_parametric.py
@@ -1,18 +1,14 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
-
-from typing import List
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 import jax.numpy as jnp
 import numpy as np
 from jax import grad, jit, vmap
 
-from adam.core.rbd_algorithms import RBDAlgorithms
 from adam.core.constants import Representations
+from adam.core.rbd_algorithms import RBDAlgorithms
 from adam.jax.jax_like import SpatialMath
 from adam.model import Model
-from adam.parametric.model import URDFParametricModelFactory, ParametricLink
+from adam.parametric.model import ParametricLink, URDFParametricModelFactory
 
 
 class KinDynComputationsParametric:
@@ -25,7 +21,7 @@ def __init__(
         urdfstring: str,
         joints_name_list: list,
         links_name_list: list,
-        root_link: str = "root_link",
+        root_link: str = None,
         gravity: np.array = jnp.array([0, 0, -9.80665, 0, 0, 0]),
     ) -> None:
         """
@@ -33,7 +29,7 @@ def __init__(
             urdfstring (str): either path or string of the urdf
             joints_name_list (list): list of the actuated joints
             links_name_list (list): list of parametric links
-            root_link (str, optional): the first link. Defaults to 'root_link'.
+            root_link (str, optional): Deprecated. The root link is automatically chosen as the link with no parent in the URDF. Defaults to None.
         """
         self.math = SpatialMath()
         self.links_name_list = links_name_list
@@ -41,6 +37,10 @@ def __init__(
         self.urdfstring = urdfstring
         self.joints_name_list = joints_name_list
         self.representation = Representations.MIXED_REPRESENTATION  # Default
+        if root_link is not None:
+            raise DeprecationWarning(
+                "The root_link argument is not used. The root link is automatically chosen as the link with no parent in the URDF"
+            )
 
     def set_frame_velocity_representation(
         self, representation: Representations
@@ -449,7 +449,7 @@ def get_total_mass(
         self.NDoF = self.rbdalgos.NDoF
         return self.rbdalgos.get_total_mass()
 
-    def get_original_densities(self) -> List[float]:
+    def get_original_densities(self) -> list[float]:
         """Returns the original densities of the parametric links
 
         Returns:
diff --git a/src/adam/parametric/model/__init__.py b/src/adam/parametric/model/__init__.py
index 176c2349..87813a22 100644
--- a/src/adam/parametric/model/__init__.py
+++ b/src/adam/parametric/model/__init__.py
@@ -1,6 +1,5 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
 from .parametric_factories.parametric_joint import ParametricJoint
 from .parametric_factories.parametric_link import ParametricLink
diff --git a/src/adam/parametric/model/parametric_factories/__init__.py b/src/adam/parametric/model/parametric_factories/__init__.py
index 6f130a0d..9947d8db 100644
--- a/src/adam/parametric/model/parametric_factories/__init__.py
+++ b/src/adam/parametric/model/parametric_factories/__init__.py
@@ -1,3 +1 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
diff --git a/src/adam/parametric/model/parametric_factories/parametric_link.py b/src/adam/parametric/model/parametric_factories/parametric_link.py
index 1346f3f8..82d2c571 100644
--- a/src/adam/parametric/model/parametric_factories/parametric_link.py
+++ b/src/adam/parametric/model/parametric_factories/parametric_link.py
@@ -1,12 +1,12 @@
+import copy
+import math
+from enum import Enum
+
 import numpy.typing as npt
 import urdf_parser_py.urdf
-from enum import Enum
-import copy
 
 from adam.core.spatial_math import SpatialMath
 from adam.model import Link
-
-import math
 from adam.model.abc_factories import Inertia, Inertial
 
 
diff --git a/src/adam/parametric/model/parametric_factories/parametric_model.py b/src/adam/parametric/model/parametric_factories/parametric_model.py
index 3702735e..8d38b226 100644
--- a/src/adam/parametric/model/parametric_factories/parametric_model.py
+++ b/src/adam/parametric/model/parametric_factories/parametric_model.py
@@ -1,11 +1,8 @@
-import pathlib
-from typing import List
-import os
-
 import urdf_parser_py.urdf
+
 from adam.core.spatial_math import SpatialMath
-from adam.model import ModelFactory, StdJoint, StdLink, Link, Joint
-from adam.model.std_factories.std_model import urdf_remove_sensors_tags, get_xml_string
+from adam.model import Joint, Link, ModelFactory, StdJoint, StdLink
+from adam.model.std_factories.std_model import get_xml_string, urdf_remove_sensors_tags
 from adam.parametric.model import ParametricJoint, ParametricLink
 
 
@@ -21,7 +18,7 @@ def __init__(
         self,
         path: str,
         math: SpatialMath,
-        links_name_list: List,
+        links_name_list: list,
         length_multiplier,
         densities,
     ):
@@ -45,26 +42,26 @@ def __init__(
         self.length_multiplier = length_multiplier
         self.densities = densities
 
-    def get_joints(self) -> List[Joint]:
+    def get_joints(self) -> list[Joint]:
         """
         Returns:
-            List[Joint]: build the list of the joints
+            list[Joint]: build the list of the joints
         """
         return [self.build_joint(j) for j in self.urdf_desc.joints]
 
-    def get_links(self) -> List[Link]:
+    def get_links(self) -> list[Link]:
         """
         Returns:
-            List[Link]: build the list of the links
+            list[Link]: build the list of the links
         """
         return [
             self.build_link(l) for l in self.urdf_desc.links if l.inertial is not None
         ]
 
-    def get_frames(self) -> List[StdLink]:
+    def get_frames(self) -> list[StdLink]:
         """
         Returns:
-            List[Link]: build the list of the links
+            list[Link]: build the list of the links
         """
         return [self.build_link(l) for l in self.urdf_desc.links if l.inertial is None]
 
diff --git a/src/adam/parametric/numpy/__init__.py b/src/adam/parametric/numpy/__init__.py
index 04b2fc09..ff573427 100644
--- a/src/adam/parametric/numpy/__init__.py
+++ b/src/adam/parametric/numpy/__init__.py
@@ -1,5 +1,4 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
 from .computations_parametric import KinDynComputationsParametric
diff --git a/src/adam/parametric/numpy/computations_parametric.py b/src/adam/parametric/numpy/computations_parametric.py
index 7e961467..f7030376 100644
--- a/src/adam/parametric/numpy/computations_parametric.py
+++ b/src/adam/parametric/numpy/computations_parametric.py
@@ -1,15 +1,12 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 import numpy as np
-from typing import List
 
-from adam.core.rbd_algorithms import RBDAlgorithms
 from adam.core.constants import Representations
+from adam.core.rbd_algorithms import RBDAlgorithms
 from adam.model import Model
-from adam.parametric.model import URDFParametricModelFactory, ParametricLink
 from adam.numpy.numpy_like import SpatialMath
+from adam.parametric.model import ParametricLink, URDFParametricModelFactory
 
 
 class KinDynComputationsParametric:
@@ -22,7 +19,7 @@ def __init__(
         urdfstring: str,
         joints_name_list: list,
         links_name_list: list,
-        root_link: str = "root_link",
+        root_link: str = None,
         gravity: np.array = np.array([0, 0, -9.80665, 0, 0, 0]),
     ) -> None:
         """
@@ -30,7 +27,7 @@ def __init__(
             urdfstring (str): either path or string of the urdf
             joints_name_list (list): list of the actuated joints
             links_name_list (list): list of parametric links
-            root_link (str, optional): the first link. Defaults to 'root_link'.
+            root_link (str, optional): Deprecated. The root link is automatically chosen as the link with no parent in the URDF. Defaults to None.
         """
         self.links_name_list = links_name_list
         self.math = SpatialMath()
@@ -38,6 +35,10 @@ def __init__(
         self.urdfstring = urdfstring
         self.joints_name_list = joints_name_list
         self.representation = Representations.MIXED_REPRESENTATION  # Default
+        if root_link is not None:
+            raise DeprecationWarning(
+                "The root_link argument is not used. The root link is automatically chosen as the link with no parent in the URDF"
+            )
 
     def set_frame_velocity_representation(
         self, representation: Representations
@@ -443,7 +444,7 @@ def get_total_mass(
         self.NDoF = model.NDoF
         return self.rbdalgos.get_total_mass()
 
-    def get_original_densities(self) -> List[float]:
+    def get_original_densities(self) -> list[float]:
         """Returns the original densities of the parametric links
 
         Returns:
diff --git a/src/adam/parametric/pytorch/__init__.py b/src/adam/parametric/pytorch/__init__.py
index 04b2fc09..ff573427 100644
--- a/src/adam/parametric/pytorch/__init__.py
+++ b/src/adam/parametric/pytorch/__init__.py
@@ -1,5 +1,4 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
 from .computations_parametric import KinDynComputationsParametric
diff --git a/src/adam/parametric/pytorch/computations_parametric.py b/src/adam/parametric/pytorch/computations_parametric.py
index 07eb7a78..63568d45 100644
--- a/src/adam/parametric/pytorch/computations_parametric.py
+++ b/src/adam/parametric/pytorch/computations_parametric.py
@@ -1,15 +1,12 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 import numpy as np
 import torch
-from typing import List
 
-from adam.core.rbd_algorithms import RBDAlgorithms
 from adam.core.constants import Representations
+from adam.core.rbd_algorithms import RBDAlgorithms
 from adam.model import Model
-from adam.parametric.model import URDFParametricModelFactory, ParametricLink
+from adam.parametric.model import ParametricLink, URDFParametricModelFactory
 from adam.pytorch.torch_like import SpatialMath
 
 
@@ -23,7 +20,7 @@ def __init__(
         urdfstring: str,
         joints_name_list: list,
         links_name_list: list,
-        root_link: str = "root_link",
+        root_link: str = None,
         gravity: np.array = torch.tensor(
             [0, 0, -9.80665, 0, 0, 0], dtype=torch.float64
         ),
@@ -33,7 +30,7 @@ def __init__(
             urdfstring (str): either path or string of the urdf
             joints_name_list (list): list of the actuated joints
             links_name_list (list): list of parametric links
-            root_link (str, optional): the first link. Defaults to 'root_link'.
+            root_link (str, optional): Deprecated. The root link is automatically chosen as the link with no parent in the URDF. Defaults to None.
         """
         self.math = SpatialMath()
         self.g = gravity
@@ -41,6 +38,10 @@ def __init__(
         self.joints_name_list = joints_name_list
         self.urdfstring = urdfstring
         self.representation = Representations.MIXED_REPRESENTATION  # Default
+        if root_link is not None:
+            raise DeprecationWarning(
+                "The root_link argument is not used. The root link is automatically chosen as the link with no parent in the URDF"
+            )
 
     def set_frame_velocity_representation(
         self, representation: Representations
@@ -447,7 +448,7 @@ def get_total_mass(
         self.NDoF = self.rbdalgos.NDoF
         return self.rbdalgos.get_total_mass()
 
-    def get_original_densities(self) -> List[float]:
+    def get_original_densities(self) -> list[float]:
         """Returns the original densities of the parametric links
 
         Returns:
diff --git a/src/adam/pytorch/__init__.py b/src/adam/pytorch/__init__.py
index 7a33bea1..b427f55a 100644
--- a/src/adam/pytorch/__init__.py
+++ b/src/adam/pytorch/__init__.py
@@ -1,7 +1,6 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
-from .computations import KinDynComputations
 from .computation_batch import KinDynComputationsBatch
+from .computations import KinDynComputations
 from .torch_like import TorchLike
diff --git a/src/adam/pytorch/computations.py b/src/adam/pytorch/computations.py
index 060a2075..3fc70805 100644
--- a/src/adam/pytorch/computations.py
+++ b/src/adam/pytorch/computations.py
@@ -1,6 +1,5 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
+
 
 import numpy as np
 import torch
@@ -18,7 +17,7 @@ def __init__(
         self,
         urdfstring: str,
         joints_name_list: list = None,
-        root_link: str = "root_link",
+        root_link: str = None,
         gravity: np.array = torch.tensor(
             [0, 0, -9.80665, 0, 0, 0], dtype=torch.float64
         ),
@@ -27,7 +26,7 @@ def __init__(
         Args:
             urdfstring (str): either path or string of the urdf
             joints_name_list (list): list of the actuated joints
-            root_link (str, optional): the first link. Defaults to 'root_link'.
+            root_link (str, optional): Deprecated. The root link is automatically chosen as the link with no parent in the URDF. Defaults to None.
         """
         math = SpatialMath()
         factory = URDFModelFactory(path=urdfstring, math=math)
@@ -35,6 +34,10 @@ def __init__(
         self.rbdalgos = RBDAlgorithms(model=model, math=math)
         self.NDoF = self.rbdalgos.NDoF
         self.g = gravity
+        if root_link is not None:
+            raise DeprecationWarning(
+                "The root_link argument is not used. The root link is automatically chosen as the link with no parent in the URDF"
+            )
 
     def set_frame_velocity_representation(
         self, representation: Representations
diff --git a/src/adam/pytorch/torch_like.py b/src/adam/pytorch/torch_like.py
index 71962f65..de2cb812 100644
--- a/src/adam/pytorch/torch_like.py
+++ b/src/adam/pytorch/torch_like.py
@@ -1,13 +1,11 @@
-# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
-# This software may be modified and distributed under the terms of the
-# GNU Lesser General Public License v2.1 or any later version.
+# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
 
 from dataclasses import dataclass
 from typing import Union
 
+import numpy as np
 import numpy.typing as ntp
 import torch
-import numpy as np
 
 from adam.core.spatial_math import ArrayLike, ArrayLikeFactory, SpatialMath
 
diff --git a/tests/conftest.py b/tests/conftest.py
index 0e9b491f..31c582bf 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,15 +1,17 @@
-import pytest
-import numpy as np
-import icub_models
-import idyntree.bindings as idyntree
-from adam import Representations
-from adam.numpy.numpy_like import SpatialMath
 import dataclasses
-from itertools import product
 import logging
 import os
+from itertools import product
+
+import icub_models
+import idyntree.bindings as idyntree
+import numpy as np
+import pytest
 import requests
 
+from adam import Representations
+from adam.numpy.numpy_like import SpatialMath
+
 
 @dataclasses.dataclass
 class State:
diff --git a/tests/parametric/test_casadi_parametric.py b/tests/parametric/test_casadi_parametric.py
index 43dbae84..b8aa4cad 100644
--- a/tests/parametric/test_casadi_parametric.py
+++ b/tests/parametric/test_casadi_parametric.py
@@ -1,8 +1,9 @@
 import casadi as cs
 import numpy as np
 import pytest
+from conftest import RobotCfg, State
+
 from adam.parametric.casadi import KinDynComputationsParametric
-from conftest import State, RobotCfg
 
 
 @pytest.fixture(scope="module")
diff --git a/tests/parametric/test_idyntree_conversion_parametric.py b/tests/parametric/test_idyntree_conversion_parametric.py
index 29c8f70d..3d7fc4ea 100644
--- a/tests/parametric/test_idyntree_conversion_parametric.py
+++ b/tests/parametric/test_idyntree_conversion_parametric.py
@@ -1,14 +1,15 @@
 import casadi as cs
 import numpy as np
 import pytest
-from adam.parametric.casadi import KinDynComputationsParametric
-from conftest import State, RobotCfg, compute_idyntree_values
+from conftest import RobotCfg, State, compute_idyntree_values
+
+from adam.model import Model
 from adam.model.conversions.idyntree import to_idyntree_model
+from adam.numpy.numpy_like import SpatialMath
+from adam.parametric.casadi import KinDynComputationsParametric
 from adam.parametric.model.parametric_factories.parametric_model import (
     URDFParametricModelFactory,
 )
-from adam.model import Model
-from adam.numpy.numpy_like import SpatialMath
 
 
 @pytest.fixture(scope="module")
diff --git a/tests/parametric/test_jax_parametric.py b/tests/parametric/test_jax_parametric.py
index f1aed86f..75780bc2 100644
--- a/tests/parametric/test_jax_parametric.py
+++ b/tests/parametric/test_jax_parametric.py
@@ -1,7 +1,8 @@
 import numpy as np
 import pytest
+from conftest import RobotCfg, State
+
 from adam.parametric.jax import KinDynComputationsParametric
-from conftest import State, RobotCfg
 
 
 @pytest.fixture(scope="module")
diff --git a/tests/parametric/test_numpy_parametric.py b/tests/parametric/test_numpy_parametric.py
index 54e2c47f..15e4ec2f 100644
--- a/tests/parametric/test_numpy_parametric.py
+++ b/tests/parametric/test_numpy_parametric.py
@@ -1,7 +1,8 @@
 import numpy as np
 import pytest
+from conftest import RobotCfg, State
+
 from adam.parametric.numpy import KinDynComputationsParametric
-from conftest import State, RobotCfg
 
 
 @pytest.fixture(scope="module")
diff --git a/tests/parametric/test_pytorch_parametric.py b/tests/parametric/test_pytorch_parametric.py
index 9ec765b7..840007c4 100644
--- a/tests/parametric/test_pytorch_parametric.py
+++ b/tests/parametric/test_pytorch_parametric.py
@@ -1,8 +1,9 @@
 import numpy as np
 import pytest
-from adam.parametric.pytorch import KinDynComputationsParametric
-from conftest import State, RobotCfg
 import torch
+from conftest import RobotCfg, State
+
+from adam.parametric.pytorch import KinDynComputationsParametric
 
 torch.set_default_dtype(torch.float64)
 
diff --git a/tests/test_casadi.py b/tests/test_casadi.py
index 466c16f9..4f213a4d 100644
--- a/tests/test_casadi.py
+++ b/tests/test_casadi.py
@@ -1,8 +1,9 @@
 import casadi as cs
 import numpy as np
 import pytest
+from conftest import RobotCfg, State
+
 from adam.casadi import KinDynComputations
-from conftest import State, RobotCfg
 
 
 @pytest.fixture(scope="module")
diff --git a/tests/test_idyntree_conversion.py b/tests/test_idyntree_conversion.py
index ea4bc1fe..ceb5f779 100644
--- a/tests/test_idyntree_conversion.py
+++ b/tests/test_idyntree_conversion.py
@@ -1,8 +1,9 @@
 import casadi as cs
 import numpy as np
 import pytest
+from conftest import RobotCfg, State, compute_idyntree_values
+
 from adam.casadi import KinDynComputations
-from conftest import State, RobotCfg, compute_idyntree_values
 from adam.model.conversions.idyntree import to_idyntree_model
 
 
diff --git a/tests/test_jax.py b/tests/test_jax.py
index 94c788e9..a74449e6 100644
--- a/tests/test_jax.py
+++ b/tests/test_jax.py
@@ -1,9 +1,10 @@
 import numpy as np
 import pytest
-from adam.jax import KinDynComputations
-from conftest import State, RobotCfg
+from conftest import RobotCfg, State
 from jax import config
 
+from adam.jax import KinDynComputations
+
 config.update("jax_enable_x64", True)
 
 
diff --git a/tests/test_numpy.py b/tests/test_numpy.py
index f5619ed2..ba3e608c 100644
--- a/tests/test_numpy.py
+++ b/tests/test_numpy.py
@@ -1,7 +1,8 @@
 import numpy as np
 import pytest
+from conftest import RobotCfg, State
+
 from adam.numpy import KinDynComputations
-from conftest import State, RobotCfg
 
 
 @pytest.fixture(scope="module")
diff --git a/tests/test_pytorch.py b/tests/test_pytorch.py
index a85c8290..2af3bbc4 100644
--- a/tests/test_pytorch.py
+++ b/tests/test_pytorch.py
@@ -1,8 +1,9 @@
 import numpy as np
 import pytest
-from adam.pytorch import KinDynComputations
-from conftest import State, RobotCfg
 import torch
+from conftest import RobotCfg, State
+
+from adam.pytorch import KinDynComputations
 
 torch.set_default_dtype(torch.float64)
 
diff --git a/tests/test_pytorch_batch.py b/tests/test_pytorch_batch.py
index 51435cb7..4839b207 100644
--- a/tests/test_pytorch_batch.py
+++ b/tests/test_pytorch_batch.py
@@ -1,10 +1,11 @@
 import numpy as np
 import pytest
-from adam.pytorch import KinDynComputationsBatch
-from conftest import State, RobotCfg
 import torch
+from conftest import RobotCfg, State
 from jax import config
 
+from adam.pytorch import KinDynComputationsBatch
+
 config.update("jax_enable_x64", True)