code: def is_inbound_message_filter(cb):
      
  
      try:
          handlers = get_magic_attr(cb)
      except AttributeError:
          return False
  
      hs = HandlerSpec(
          (_apply_inbound_message_filter, ())
      )
  
      return hs in handlers
docs: Return true if `cb` has been decorated with :func:`inbound_message_filter`.