gh-40864: remove deprecated function in plot3d/texture
    
from File: src/sage/plot/plot3d/texture.py ; PR: #27593 ; Closed Date:
2020-08-23

also cleanup of th modified file


### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
    
URL: #40864
Reported by: Frédéric Chapoton
Reviewer(s): David Coudert

Author: Release Manager

src/sage/plot/plot3d/texture.py

@@ -36,9 +36,8 @@
 
 from sage.misc.classcall_metaclass import ClasscallMetaclass, typecall
 from sage.misc.fast_methods import WithEqualityById
-from sage.structure.sage_object import SageObject
-
 from sage.plot.colors import colors, Color
+from sage.structure.sage_object import SageObject
 
 
 uniq_c = 0
@@ -57,25 +56,7 @@ def _new_global_texture_id():
     """
     global uniq_c
     uniq_c += 1
-    return "texture%s" % uniq_c
-
-
-def is_Texture(x):
-    r"""
-    Deprecated. Use ``isinstance(x, Texture)`` instead.
-
-    EXAMPLES::
-
-        sage: from sage.plot.plot3d.texture import is_Texture, Texture
-        sage: t = Texture(0.5)
-        sage: is_Texture(t)
-        doctest:...: DeprecationWarning: Please use isinstance(x, Texture)
-        See https://github.com/sagemath/sage/issues/27593 for details.
-        True
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(27593, "Please use isinstance(x, Texture)")
-    return isinstance(x, Texture)
+    return f"texture{uniq_c}"
 
 
 def parse_color(info, base=None):
@@ -124,21 +105,22 @@ def parse_color(info, base=None):
     """
     if isinstance(info, Color):
         return info.rgb()
-    elif isinstance(info, str):
+    if isinstance(info, str):
         try:
             return Color(info)
         except KeyError:
-            raise ValueError("unknown color '%s'" % info)
-    else:
-        r, g, b = base
-        # We don't want to lose the data when we split it into its respective components.
-        if not r:
-            r = 1e-5
-        if not g:
-            g = 1e-5
-        if not b:
-            b = 1e-5
-        return (float(info * r), float(info * g), float(info * b))
+            raise ValueError(f"unknown color '{info}'")
+
+    r, g, b = base
+    # We don't want to lose the data when we split it into its
+    # respective components.
+    if not r:
+        r = 1e-5
+    if not g:
+        g = 1e-5
+    if not b:
+        b = 1e-5
+    return (float(info * r), float(info * g), float(info * b))
 
 
 class Texture(WithEqualityById, SageObject, metaclass=ClasscallMetaclass):
@@ -278,7 +260,7 @@ def __classcall__(cls, id=None, **kwds):
         return typecall(cls, id, **kwds)
 
     def __init__(self, id, color=(.4, .4, 1), opacity=1, ambient=0.5,
-                 diffuse=1, specular=0, shininess=1, name=None, **kwds):
+                 diffuse=1, specular=0, shininess=1, name=None, **kwds) -> None:
         r"""
         Construction of a texture.
 
@@ -321,7 +303,7 @@ def __init__(self, id, color=(.4, .4, 1), opacity=1, ambient=0.5,
             specular = parse_color(specular, color)
         self.specular = specular
 
-    def _repr_(self):
+    def _repr_(self) -> str:
         """
         Return a string representation of the Texture object.
 
@@ -338,7 +320,7 @@ def _repr_(self):
         else:
             return f"Texture({self.id}, {self.hex_rgb()})"
 
-    def hex_rgb(self):
+    def hex_rgb(self) -> str:
         """
         EXAMPLES::
 
@@ -350,7 +332,7 @@ def hex_rgb(self):
         """
         return "{:02x}{:02x}{:02x}".format(*tuple(int(255 * s) for s in self.color))
 
-    def tachyon_str(self):
+    def tachyon_str(self) -> str:
         r"""
         Convert Texture object to string suitable for Tachyon ray tracer.
 
@@ -383,7 +365,7 @@ def tachyon_str(self):
                                    diffuse=diffuse, specular=specular,
                                    opacity=self.opacity, color=self.color)
 
-    def x3d_str(self):
+    def x3d_str(self) -> str:
         r"""
         Convert Texture object to string suitable for x3d.
 
@@ -402,7 +384,7 @@ def x3d_str(self):
             "</Appearance>").format(color=self.color, shininess=self.shininess,
                                     specular=self.specular[0])
 
-    def mtl_str(self):
+    def mtl_str(self) -> str:
         r"""
         Convert Texture object to string suitable for mtl output.
 
@@ -426,7 +408,7 @@ def mtl_str(self):
                                illumination=(2 if sum(self.specular) > 0 else 1),
                                shininess=self.shininess, opacity=self.opacity)
 
-    def jmol_str(self, obj):
+    def jmol_str(self, obj) -> str:
         r"""
         Convert Texture object to string suitable for Jmol applet.