class_docstr: The worker context class.
  
  This context object provides configuration information for each task. One
  context manager with a worker context object will be created per
  invocation to the `worker_fn` where `get_current_worker_context` can be called
  to access the worker context object.
docstr: Returns whether the task is a chief node.
docstr_tok: ["Returns","whether","the","task","is","a","chief","node","."]
code: def is_chief(self):
      """Returns whether the task is a chief node."""
      return self._is_chief_node
  
imports: import copy
  import json
  import os
  import threading
  import time
  from tensorflow.core.protobuf import config_pb2
  from tensorflow.python.client import session
  from tensorflow.python.distribute import distribute_coordinator_context
  from tensorflow.python.distribute import multi_worker_util
  from tensorflow.python.platform import tf_logging
  from tensorflow.python.training import coordinator
  from tensorflow.python.training import monitored_session
  from tensorflow.python.training import server_lib
label_desc: Use image node_id 16 for calling the _WorkerContext obj's underlying member method code with example usage: obj.is_chief() and returns: self