Add additionalProperties handling in python code genrator by adding dictionary handling in model's to_dict() method

modules/swagger-codegen/src/main/resources/python/model.mustache

@@ -95,6 +95,11 @@ class {{classname}}(object):
                     lambda x: x.to_dict() if hasattr(x, "to_dict") else x,
                     value
                 ))
+            elif isinstance(value, dict):
+                result[attr] = dict(map(
+                    lambda (k, v): (k, v.to_dict()) if hasattr(v, "to_dict") else (k, v),
+                    value.iteritems()
+                    ))
             elif hasattr(value, "to_dict"):
                 result[attr] = value.to_dict()
             else:
@@ -114,14 +119,14 @@ class {{classname}}(object):
         """
         return self.to_str()
 
-    def __eq__(self, other): 
+    def __eq__(self, other):
         """
         Returns true if both objects are equal
         """
         return self.__dict__ == other.__dict__
 
     def __ne__(self, other):
-        """ 
+        """
         Returns true if both objects are not equal
         """
         return not self == other