Add missing dunder method - __ne__ to the class GridFSProxy class

Author: srinivasreddy

mongoengine/fields.py

@@ -1465,6 +1465,9 @@ def __eq__(self, other):
         else:
             return False
 
+    def __ne__(self, other):
+        return not self == other
+
     @property
     def fs(self):
         if not self._fs: