code: def is_chief(cluster_spec=None, task_type=None, task_id=None):
      """Returns whether the given task is chief in the cluster.
  
      Since there is at most one evaluator and the evaluator itself should be
      independent of the training cluster, the evaluator job is also a chief job on
      its own.
  
      If this is currently running under a `_WorkerContext` of distribute
      coordinator, the arguments can be omitted as the result is already available.
  
      Args:
        cluster_spec: a dict, `ClusterDef` or `ClusterSpec` object specifying the
          cluster configurations.
        task_type: the task type in the cluster.
        task_id: the task id in the cluster.
  
      Returns:
        a boolean indicating whether the given task is chief.
  
      Raises:
        ValueError: if `task_type` is not in the `cluster_spec` or `task_id` exceeds
          the maximum id of the `task_type`.
      """
      if has_worker_context():
          # If a worker context exists, use the value provided by it.
          return dc_context.get_current_worker_context().is_chief
  
      _validate_cluster_spec(cluster_spec, task_type, task_id)
      cluster_spec = normalize_cluster_spec(cluster_spec).as_dict()
  
      if task_type == "chief" or task_type == "evaluator":
          return True
  
      # If chief not in the cluster_spec, use the first worker as chief. This is
      # common in CollectiveAllReduceStrategy.
      if (
          "chief" not in cluster_spec
          and task_type == "worker"
          and task_id == 0
      ):
          return True
      return False
  
file_path: tensorflow-upstream/tensorflow/python/distribute/multi_worker_util.py
imports: from tensorflow.core.protobuf import cluster_pb2
  from tensorflow.python.distribute import distribute_coordinator_context
  from tensorflow.python.training import server_lib
label_desc: Use image node_id 4 for calling a global function with example usage: is_chief(cluster_spec, task_type, task_id) and returns: False, dc_context, True, True