code: def depfilter(class_, filter_name):
      
      spec = _depfilter_spec(class_, filter_name)
  
      def decorator(f):
          add_handler_spec(
              f,
              spec,
          )
          return f
  
      return decorator
docs: Register the decorated method at the addressed :class:`~.callbacks.Filter`
      on a class on which the service depends.
  
      :param class_: A service class which is listed in the
                     :attr:`~.Meta.ORDER_AFTER` relationship.
      :type class_: :class:`Service` class or
                    :class:`aioxmpp.stream.StanzaStream`
      :param filter_name: Attribute name of the filter to register at
      :type filter_name: :class:`str`
  
      The filter at which the decorated method is registered is discovered by
      accessing the attribute with the name `filter_name` on the instance of the
      dependent class `class_`. If `class_` is
      :class:`aioxmpp.stream.StanzaStream`, the filter is searched for on the
      stream (and no dependendency needs to be declared).
  
      .. versionadded:: 0.9