code: def application_id(self):
      return self._application_id
  
file_path: mars/mars/deploy/yarn/client.py
imports: import logging
  import random
  import time
  import uuid
  from ...session import new_session
  from ...utils import to_str, calc_size_by_str
  from ..utils import wait_services_ready
  from .config import MarsApplicationConfig, MarsSupervisorConfig, MarsWorkerConfig
label_desc: Use image node_id 4 for calling the YarnClusterClient obj's underlying member method code with example usage: obj.application_id() and returns: self