message: MWMS tutorial: Update is_chief function with a note.
diff: @@ -34,8 +34,14 @@ NUM_STEPS_PER_EPOCH = 50
  def _is_chief(task_type, task_id):
  - return task_type is None or task_type == 'chief' or (task_type == 'worker' and
  - task_id == 0)
  + # Note: there are two possible `TF_CONFIG` configuration.
  + # 1) In addition to `worker` tasks, a `chief` task type is use;
  + # in this case, this function should be modified to
  + # `return task_type == 'chief'`.
  + # 2) Only `worker` task type is used; in this case, worker 0 is
  + # regarded as the chief. The implementation demonstrated here
  + # is for this case.
  + return task_type == 'worker' and task_id == 0
  def _get_temp_dir(dirpath, task_id):
  