code: def _shutdown_servers():
      set_initialized(False)
      # send ShutDownRequest to servers
      if rpc.get_rank() == 0:  # Only client_0 issue this command
          req = rpc.ShutDownRequest(rpc.get_rank())
          for server_id in range(rpc.get_num_server()):
              rpc.send_request(server_id, req)
  
imports: import atexit
  import gc
  import multiprocessing
  import os
  import queue
  import sys
  import time
  import traceback
  from enum import Enum
  from ..None import utils
  from ..base import dgl_warning, DGLError
  from .None import rpc
  from .constants import MAX_QUEUE_SIZE
  from .kvstore import close_kvstore, init_kvstore
  from .role import init_role
  from .rpc_client import connect_to_server
label_desc: Use image node_id 11 for calling a global function with example usage: _shutdown_servers() without return types