Merge branch 'patch-8' of https://github.com/wpjunior/mongoengine

mongoengine/fields.py

@@ -734,6 +734,9 @@ class GenericReferenceField(BaseField):
     def to_mongo(self, document):
         if document is None:
             return None
+        
+        if isinstance(document, (dict, SON)):
+            return document                         
 
         id_field_name = document.__class__._meta['id_field']
         id_field = document.__class__._fields[id_field_name]