code: def is_depfilter_handler(class_, filter_name, filter_):
      
      try:
          handlers = get_magic_attr(filter_)
      except AttributeError:
          return False
  
      return _depfilter_spec(class_, filter_name) in handlers
docs: Return true if `filter_` has been decorated with :func:`depfilter` for the
      given filter and class.