code: def __str__(self) -> str:
      return f"<_TopicPair namespace={self.namespace}, send={self.send}, receive={self.receive}>"
  
imports: import json
  import typing
  from logging import getLogger
  from fate.arch.federation.api import PartyMeta
  from fate.arch.federation.backends.osx import osx_pb2
  from fate.arch.federation.message_queue import MessageQueueBasedFederation
  from ._mq_channel import MQChannel
label_desc: Use image node_id 2 for calling the _TopicPair obj's underlying member method code with example usage: obj.__str__() and returns: str, self, str, self, str, self, str