diff --git a/.travis.yml b/.travis.yml
index 72ac06d..1de12e2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,9 +12,6 @@ git:
 jobs:
   include:
     - stage: test
-      python: "2.7"
-      script: sh test.sh
-      if: env(deploy) IS NOT present
     - # stage name not required
       python: "3.4"
       script: sh test.sh
diff --git a/README.rst b/README.rst
index dd29262..3c1252c 100644
--- a/README.rst
+++ b/README.rst
@@ -8,7 +8,7 @@ applications.
 System Requirements
 -------------------
 
-The SDK currently supports Python 2.7, 3.4, 3.5, 3.6, pypy, and pypy3.
+The SDK currently supports Python 3.4, 3.5, 3.6, pypy, and pypy3.
 The following packages are required.
 
 -  `requests <https://pypi.python.org/pypi/requests>`__
diff --git a/setup.py b/setup.py
index 50d2053..788c938 100644
--- a/setup.py
+++ b/setup.py
@@ -54,7 +54,6 @@ def run_tests(self):
         'Operating System :: OS Independent',
         'License :: OSI Approved :: Apache Software License',
         'Programming Language :: Python',
-        'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
diff --git a/smartsheet-sdk-tests b/smartsheet-sdk-tests
new file mode 160000
index 0000000..8044e89
--- /dev/null
+++ b/smartsheet-sdk-tests
@@ -0,0 +1 @@
+Subproject commit 8044e8962393e0bcb5e1f250ca7d84f837cbd213
diff --git a/smartsheet/models/date_object_value.py b/smartsheet/models/date_object_value.py
index ed20abd..ff450c3 100644
--- a/smartsheet/models/date_object_value.py
+++ b/smartsheet/models/date_object_value.py
@@ -26,9 +26,9 @@
 class DateObjectValue(ObjectValue):
     """Smartsheet DateObjectValue data model."""
 
-    def __init__(self, props=None, object_type=None, base_obj=None):
+    def __init__(self, props=None, base_obj=None):
         """Initialize the DateObjectValue model."""
-        super(DateObjectValue, self).__init__(object_type, base_obj)
+        super(DateObjectValue, self).__init__(base_obj)
         self._base = None
         if base_obj is not None:
             self._base = base_obj
@@ -50,5 +50,5 @@ def value(self, value):
             self._value = value
         else:
             if isinstance(value, six.string_types):
-                value = parse(value)
+                value = parse(value).date()
                 self._value = value
diff --git a/smartsheet/models/datetime_object_value.py b/smartsheet/models/datetime_object_value.py
new file mode 100644
index 0000000..828c956
--- /dev/null
+++ b/smartsheet/models/datetime_object_value.py
@@ -0,0 +1,55 @@
+
+# pylint: disable=C0111,R0902,R0904,R0912,R0913,R0915,E1101
+# Smartsheet Python SDK.
+#
+# Copyright 2018Smartsheet.com, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"): you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from __future__ import absolute_import
+
+from .object_value import *
+from ..util import deserialize
+from datetime import datetime
+from dateutil.parser import parse
+
+
+class DatetimeObjectValue(ObjectValue):
+    """Smartsheet DateObjectValue data model."""
+
+    def __init__(self, props=None, object_type=None, base_obj=None):
+        """Initialize the DateObjectValue model."""
+        super(DatetimeObjectValue, self).__init__(object_type, base_obj)
+        self._base = None
+        if base_obj is not None:
+            self._base = base_obj
+
+        self._value = None
+
+        if props:
+            deserialize(self, props)
+
+        self.__initialized = True
+
+    @property
+    def value(self):
+        return self._value
+
+    @value.setter
+    def value(self, value):
+        if isinstance(value, datetime):
+            self._value = value
+        else:
+            if isinstance(value, six.string_types):
+                value = parse(value)
+                self._value = value
\ No newline at end of file
diff --git a/smartsheet/models/sheet.py b/smartsheet/models/sheet.py
index b3f457f..70c846b 100644
--- a/smartsheet/models/sheet.py
+++ b/smartsheet/models/sheet.py
@@ -20,6 +20,7 @@
 from .attachment import Attachment
 from .column import Column
 from .sheet_filter import SheetFilter
+from .sheet_form import SheetForm
 from .comment import Comment
 from .contact_object_value import ContactObjectValue
 from .cross_sheet_reference import CrossSheetReference
@@ -61,6 +62,7 @@ def __init__(self, props=None, base_obj=None):
         self._effective_attachment_options = EnumeratedList(AttachmentType)
         self._favorite = Boolean()
         self._filters = TypedList(SheetFilter)
+        self._forms = TypedList(SheetForm)
         self._from_id = Number()
         self._gantt_enabled = Boolean()
         self._has_summary_fields = Boolean()
@@ -190,6 +192,14 @@ def filters(self):
     def filters(self, value):
         self._filters.load(value)
 
+    @property
+    def forms(self):
+        return self._forms
+
+    @forms.setter
+    def forms(self, value):
+        self._forms.load(value)
+
     @property
     def from_id(self):
         return self._from_id.value
diff --git a/smartsheet/models/sheet_form.py b/smartsheet/models/sheet_form.py
new file mode 100644
index 0000000..44ecbe6
--- /dev/null
+++ b/smartsheet/models/sheet_form.py
@@ -0,0 +1,115 @@
+# pylint: disable=C0111,R0902,R0904,R0912,R0913,R0915,E1101
+# Smartsheet Python SDK.
+#
+# Copyright 2017 Smartsheet.com, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"): you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from __future__ import absolute_import
+
+from ..types import *
+from ..util import serialize
+from ..util import deserialize
+
+
+class SheetForm(object):
+
+    """Smartsheet SheetForm data model."""
+
+    def __init__(self, props=None, base_obj=None):
+        """Initialize the SheetForm model."""
+        self._base = None
+        if base_obj is not None:
+            self._base = base_obj
+
+        self._id = Number()
+        self._publish_type = String()
+        self._publish_key = String()
+        self._publish_url = String()
+        self._title = String()
+        self._published = Boolean()
+
+        if props:
+            deserialize(self, props)
+
+        self.request_response = None
+        self.__initialized = True
+
+    # def __getattr__(self, key):
+    #     if key == 'id':
+    #         return self.id_
+    #     else:
+    #         raise AttributeError(key)
+
+    # def __setattr__(self, key, value):
+    #     if key == 'id':
+    #         self.id_ = value
+    #     else:
+    #         super(SheetForm, self).__setattr__(key, value)
+
+    @property
+    def id(self):
+        return self._id
+
+    @id.setter
+    def id(self, value):
+        self._id.value = value
+
+    @property
+    def publish_type(self):
+        return self._publish_type.value
+
+    @publish_type.setter
+    def publish_type(self, value):
+        self._publish_type.value = value
+
+    @property
+    def publish_key(self):
+        return self._publish_key.value
+
+    @publish_key.setter
+    def publish_key(self, value):
+        self._publish_key.value = value
+
+    @property
+    def publish_url(self):
+        return self._publish_url
+
+    @publish_url.setter
+    def publish_url(self, value):
+        self._publish_url.value = value
+
+    @property
+    def title(self):
+        return self._title
+
+    @title.setter
+    def title(self, value):
+        self._title.value = value
+
+    @property
+    def published(self):
+        return self._published
+
+    @published.setter
+    def published(self, value):
+        self._published.value = value
+
+    def to_dict(self):
+        return serialize(self)
+
+    def to_json(self):
+        return json.dumps(self.to_dict())
+
+    def __str__(self):
+        return self.to_json()
\ No newline at end of file
diff --git a/smartsheet/object_value.py b/smartsheet/object_value.py
index ada13e7..a7b2aea 100644
--- a/smartsheet/object_value.py
+++ b/smartsheet/object_value.py
@@ -17,6 +17,7 @@
 from .models.boolean_object_value import BooleanObjectValue
 from .models.contact_object_value import ContactObjectValue
 from .models.date_object_value import DateObjectValue
+from .models.datetime_object_value import DatetimeObjectValue
 from .models.duration import Duration
 from .models.multi_contact_object_value import MultiContactObjectValue
 from .models.multi_picklist_object_value import MultiPicklistObjectValue
@@ -40,9 +41,11 @@ def assign_to_object_value(value):
                 return PredecessorList(value)
             elif enum_object_type == CONTACT:
                 return ContactObjectValue(value)
-            elif enum_object_type == DATE or enum_object_type == DATETIME or \
+            elif enum_object_type == DATE:
+                return DateObjectValue(value)
+            elif enum_object_type == DATETIME or \
                     enum_object_type == ABSTRACT_DATETIME:
-                return DateObjectValue(value, enum_object_value_type)
+                return DatetimeObjectValue(value, enum_object_value_type)
             elif enum_object_type == MULTI_CONTACT:
                 return MultiContactObjectValue(value)
             elif enum_object_type == MULTI_PICKLIST:
diff --git a/smartsheet/session.py b/smartsheet/session.py
index 7305589..443075e 100644
--- a/smartsheet/session.py
+++ b/smartsheet/session.py
@@ -50,7 +50,7 @@ def pinned_session(pool_maxsize=8):
     http_adapter = _SSLAdapter(pool_connections=4,
                                pool_maxsize=pool_maxsize,
                                max_retries=Retry(total=1,
-                                                 method_whitelist=Retry.DEFAULT_METHOD_WHITELIST.union(['POST'])))
+                                                 allowed_methods=Retry.DEFAULT_ALLOWED_METHODS.union(['POST'])))
 
     _session = requests.session()
     _session.hooks = {'response': redact_token}
diff --git a/smartsheet/sheets.py b/smartsheet/sheets.py
index 0d0e67e..7c610ef 100644
--- a/smartsheet/sheets.py
+++ b/smartsheet/sheets.py
@@ -430,7 +430,7 @@ def get_row(self, sheet_id, row_id, include=None, exclude=None):
                 flags that indicate additional attributes to be included in
                 each Row object within the response. Valid list values:
                 discussions, attachments, format, filters, columnType,
-                rowPermalink, rowWriterInfo.
+                rowPermalink, rowPropertyReleaseFlag, rowWriterInfo.
             exclude (str): Response will not include cells
                 that have never contained any data.
 
diff --git a/smartsheet/smartsheet.py b/smartsheet/smartsheet.py
index e67be7c..1de3a09 100644
--- a/smartsheet/smartsheet.py
+++ b/smartsheet/smartsheet.py
@@ -173,6 +173,7 @@ def __init__(self, access_token=None, max_connections=8,
         self._assume_user = None
         self._test_scenario_name = None
         self._change_agent = None
+        self._custom_properties = None
 
     def assume_user(self, email=None):
         """Assume identity of specified user.
@@ -218,11 +219,20 @@ def with_change_agent(self, change_agent):
         """
         Request headers will contain the 'Smartsheet-Change-Agent' header value
 
-        Agrs:
+        Args:
             change_agent: (str) the name of this change agent
         """
         self._change_agent = change_agent
 
+    def with_custom_properties(self, custom_properties):
+        """
+        Request headers will contain custom header values defined in the 'custom_properties'
+
+        Args:
+            'custom_properties': (dict) the dictionary of custom headers
+        """
+        self._custom_properties = custom_properties
+
     def request(self, prepped_request, expected, operation):
         """
         Make a request from the Smartsheet API.
@@ -416,6 +426,11 @@ def prepare_request(self, _op):
             except KeyError:
                 pass
 
+        if self._custom_properties is not None:
+            for custom_property in self._custom_properties:
+                prepped_request.headers.update(
+                    {custom_property: self._custom_properties[custom_property]})
+
         return prepped_request
 
     def __getattr__(self, name):
diff --git a/smartsheet/token.py b/smartsheet/token.py
index c67588b..397c26e 100644
--- a/smartsheet/token.py
+++ b/smartsheet/token.py
@@ -20,6 +20,7 @@
 import logging
 from . import fresh_operation
 
+import hashlib
 
 class Token(object):
 
@@ -69,6 +70,45 @@ def get_access_token(self, client_id, code, _hash, redirect_uri=None):
 
         return response
 
+    def get_access_token(self, client_id, code, client_secret, redirect_uri=None):
+        """Get an access token, as part of the OAuth process. For more
+        information, see [OAuth
+        Flow](http://smartsheet-platform.github.io/api-docs/index.html#oauth-flow)
+
+        Args:
+            client_id (str)
+            code (str)
+            _client_secret (str): Plain text of your `app_secret`.
+            redirect_uri (str): Redirect URL registered for
+                your app, including protocol (e.g. \"http://\"); if not
+                provided, the redirect URL set during registration is used.
+
+        Returns:
+            AccessToken
+        """
+        if not all(val is not None for val in ['client_id', 'code', 'client_secret']):
+            raise ValueError(
+                ('One or more required values '
+                 'are missing from call to ' + __name__))
+        app_secret = hashlib.sha256(client_secret + '|' + code)
+
+        _op = fresh_operation('get_access_token')
+        _op['method'] = 'POST'
+        _op['path'] = '/token'
+        _op['form_data'] = {}
+        _op['form_data']['grant_type'] = 'authorization_code'
+        _op['form_data']['client_id'] = client_id
+        _op['form_data']['code'] = code
+        _op['form_data']['redirect_uri'] = redirect_uri
+        _op['form_data']['hash'] = app_secret
+        _op['auth_settings'] = None
+
+        expected = 'AccessToken'
+        prepped_request = self._base.prepare_request(_op)
+        response = self._base.request(prepped_request, expected, _op)
+
+        return response
+
     def refresh_access_token(self, client_id, refresh_token, _hash,
                              redirect_uri=None):
         """Refresh an access token, as part of the OAuth process. For more
@@ -109,6 +149,47 @@ def refresh_access_token(self, client_id, refresh_token, _hash,
 
         return response
 
+    def refresh_access_token(self, client_id, refresh_token, client_secret,
+                             redirect_uri=None):
+        """Refresh an access token, as part of the OAuth process. For more
+        information, see [OAuth
+        Flow](http://smartsheet-platform.github.io/api-docs/index.html#oauth-flow)
+
+        Args:
+            client_id (str)
+            refresh_token (str)
+            client_secret (str): Plain text of your `app_secret`
+            redirect_uri (str): Redirect URL registered for
+                your app, including protocol (e.g. \"http://\"); if not
+                provided, the redirect URL set during registration is used.
+
+        Returns:
+            AccessToken
+        """
+        if not all(val is not None for val in ['client_id', 'refresh_token',
+                                               'client_secret']):
+            raise ValueError(
+                ('One or more required values '
+                 'are missing from call to ' + __name__))
+
+        app_secret = hashlib.sha256(client_secret + '|' + code)
+
+        _op = fresh_operation('refresh_access_token')
+        _op['method'] = 'POST'
+        _op['path'] = '/token'
+        _op['form_data'] = {}
+        _op['form_data']['grant_type'] = 'refresh_token'
+        _op['form_data']['client_id'] = client_id
+        _op['form_data']['refresh_token'] = refresh_token
+        _op['form_data']['redirect_uri'] = redirect_uri
+        _op['form_data']['hash'] = app_secret
+
+        expected = 'AccessToken'
+        prepped_request = self._base.prepare_request(_op)
+        response = self._base.request(prepped_request, expected, _op)
+
+        return response
+
     def revoke_access_token(self):
         """Revoke the access token used to make the request.
 
diff --git a/smartsheet/types.py b/smartsheet/types.py
index 598e42c..9cdd2fd 100644
--- a/smartsheet/types.py
+++ b/smartsheet/types.py
@@ -15,7 +15,6 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import collections
 import importlib
 import json
 import logging
@@ -25,8 +24,12 @@
 from dateutil.parser import parse
 from enum import Enum
 
+try:
+    from collections.abc import MutableSequence
+except ImportError:
+    from collections import MutableSequence
 
-class TypedList(collections.MutableSequence):
+class TypedList(MutableSequence):
 
     def __init__(self, item_type):
         self.item_type = item_type
@@ -281,7 +284,7 @@ def set(self, value):
             self._value = None
 
     def __eq__(self, other):
-        if isinstance(other, Enum):
+        if isinstance(other, Enum) or other is None:
             return self._value == other
         elif isinstance(other, six.string_types):
             return self._value == self.__enum[other]