code: def target(self, hosts):
          
          if self.__is_retargeted:
              raise TypeError('Cannot use target more than once.')
          rv = FanoutClient(hosts, connection_pool=self.connection_pool,
                            max_concurrency=self._max_concurrency)
          rv._cb_poll = self._cb_poll
          rv.__is_retargeted = True
          return rv
docs: Temporarily retarget the client for one call.  This is useful
          when having to deal with a subset of hosts for one call.