code: def job_name() -> str:
      """Returns the job name used by all clients in this DTensor cluster."""
      # If missing, assumes the program runs locally and use localhost as job name
      # per TensorFlow convention.
      return os.environ.get(
          _DT_JOB_NAME, "localhost" if num_clients() == 1 else "worker"
      )
  
imports: import os
  from typing import List, Optional, Union
  from tensorflow.python.eager import context
  from tensorflow.python.framework import config
  from tensorflow.python.framework import device
  from tensorflow.python.util.tf_export import tf_export
label_desc: Use image node_id 6 for calling a global function with example usage: job_name() and returns: os