          Deserialize a dictionary of attributes into an object instance.
          You should override this method to control how deserialized objects
          are instantiated.
          """
          removed_relations = []
  
          # Deleted related objects
          if self._deleted:
              removed_relations = list(self._deleted)
  
          if instance is not None:
              instance.update(attrs)
              instance._removed_relations = removed_relations
              return instance
          return attrs
 
</s> remove             instance._removed_relations = removed_relations
 </s> add  </s> remove         # Deleted related objects
        if self._deleted:
            removed_relations = list(self._deleted)

 </s> add  </s> remove                 ret = []
 </s> add                 ret = RelationsList() </s> remove         instance._removed_relations = removed_relations
 </s> add  </s> remove         self._deleted = None
 </s> add 
          Deserialize a dictionary of attributes into an object instance.
          You should override this method to control how deserialized objects
          are instantiated.
          """






          if instance is not None:
              instance.update(attrs)
              instance._removed_relations = removed_relations
              return instance
          return attrs
keep keep keep keep replace replace replace replace replace replace keep keep keep keep keep
 Fix model serializer nestesd delete behavior 
rest_framework/serializers.py