code: def _create_id(self, hostname, local_rank):
      return "{}:{}".format(hostname, local_rank)
  
imports: import os
  import threading
  from enum import IntFlag
  from horovod.runner.common.util import network, secret
  from horovod.runner.elastic.rendezvous import PUT_WORKER_ADDRESSES
  from horovod.runner.http.http_client import put_data_into_kvstore
label_desc: Use image node_id 6 for calling the WorkerNotificationManager obj's underlying member method code with example usage: obj._create_id(hostname, local_rank) and returns: str