code: def client_id() -> int:
      """Returns this client's ID."""
      # If missing, assume running with a single client with client_id of 0.
      client_id_value = int(os.environ.get(_DT_CLIENT_ID, "0"))
      if client_id_value < 0:
          raise ValueError(
              f"Environment variable {_DT_CLIENT_ID} "
              f"must be >= 0, got {client_id_value}. "
          )
      if client_id_value >= num_clients():
          raise ValueError(
              f"Environment variable {_DT_CLIENT_ID} "
              f"must be < {num_clients()}, got {client_id_value}"
          )
      return client_id_value
  
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 4 for calling a global function with example usage: client_id() and returns: client_id_value