code: def root_topic(self):
      """this is a property, in case the handler is created
      before the engine gets registered with an id"""
      if isinstance(getattr(self.engine, "id", None), int):
          return "engine.%i" % self.engine.id
      else:
          return "engine"
  
imports: from zmq.log.handlers import PUBHandler
label_desc: Use image node_id 2 for calling the EnginePUBHandler obj's underlying member method code with example usage: obj.root_topic() and returns: unknown, str