Avoid DeprecationWarning when importing OrderedDict

in flask_restx/model.py and flask_restx/swagger.py logic is installed to
circumvent differences in Python2 and Python3 when importing from the
collections module. Some classes from collections has been moved to
collections.abc in Python3. OrderedDict is not one of them, hence an
ImportError is raised when trying to import OrderedDict from
collections.abc. This then leads to importing both OrderedDict AND
MutableMapping/Hashable from collections.abc which then raises a
deprecation warning since MutableMapping/Hashable lives in
collections.abc in Python3.

This patch should fix those DeprecationWarnings to be raised.

flask_restx/model.py

@@ -5,11 +5,12 @@
 import re
 import warnings
 
+from collections import OrderedDict
 try:
-    from collections.abc import OrderedDict, MutableMapping
+    from collections.abc import MutableMapping
 except ImportError:
     # TODO Remove this to drop Python2 support
-    from collections import OrderedDict, MutableMapping
+    from collections import MutableMapping
 from six import iteritems, itervalues
 from werkzeug.utils import cached_property
 

flask_restx/swagger.py

@@ -5,11 +5,12 @@
 import re
 
 from inspect import isclass, getdoc
+from collections import OrderedDict
 try:
-    from collections.abc import OrderedDict, Hashable
+    from collections.abc import Hashable
 except ImportError:
     # TODO Remove this to drop Python2 support
-    from collections import OrderedDict, Hashable
+    from collections import Hashable
 from six import string_types, itervalues, iteritems, iterkeys
 
 from flask import current_app