code: def __init__(self, pool_address: str, watch_ref: mo.ActorRef = None):
      self._pool_address = pool_address
      self._watch_ref = watch_ref
  
imports: import asyncio
  import logging
  import os
  import signal
  import uuid
  from collections import defaultdict
  from typing import AsyncGenerator, Dict, List, Optional, TypeVar
  from ...None import oscar
  from ...services import NodeRole
  from ...services.cluster.backends import register_cluster_backend, AbstractClusterBackend
  from ...utils import to_binary, to_str
  from ..utils import wait_all_supervisors_ready
  from .config import MarsSupervisorConfig, MarsWorkerConfig
label_desc: Use image node_id 1 to create a new YarnClusterBackend object from inherited base classes: AbstractClusterBackend with example: obj = YarnClusterBackend(pool_address, watch_ref)