      _dict_class = SortedDictWithMetadata
  
      def __init__(self, instance=None, data=None, files=None,
                   context=None, partial=False, many=None,
                   allow_delete=False, **kwargs):
          super(BaseSerializer, self).__init__(**kwargs)
          self.opts = self._options_class(self.Meta)
          self.parent = None
          self.root = None
          self.partial = partial
 
</s> remove         self.allow_delete = allow_delete
 </s> add         self.allow_add_remove = allow_add_remove
                 allow_add_remove=False, **kwargs):
      _dict_class = SortedDictWithMetadata
  
      def __init__(self, instance=None, data=None, files=None,
                   context=None, partial=False, many=None,
                 allow_add_remove=False, **kwargs):
          super(BaseSerializer, self).__init__(**kwargs)
          self.opts = self._options_class(self.Meta)
          self.parent = None
          self.root = None
          self.partial = partial
keep keep keep keep replace keep keep keep keep keep
 one-many writable nested modelserializer support 
rest_framework/serializers.py