code: def test_multi_client():
      reset_envs()
      os.environ["DGL_DIST_MODE"] = "distributed"
      ip_config = "rpc_ip_config_mul_client.txt"
      generate_ip_config(ip_config, 1, 1)
      ctx = mp.get_context("spawn")
      num_clients = 20
      pserver = ctx.Process(
          target=start_server,
          args=(num_clients, ip_config, 0, 1),
      )
      pclient_list = []
      for i in range(num_clients):
          pclient = ctx.Process(
              target=start_client, args=(ip_config, 0, 1)
          )
          pclient_list.append(pclient)
      pserver.start()
      for i in range(num_clients):
          pclient_list[i].start()
      for i in range(num_clients):
          pclient_list[i].join()
      pserver.join()
  
imports: import multiprocessing
  import os
  import socket
  import time
  import unittest
  import backend
  import dgl
  import pytest
  from numpy.testing import assert_array_equal
  from utils import generate_ip_config, reset_envs
label_desc: Use image node_id 9 for calling a global function with example usage: test_multi_client() without return types