code: def test_exception_single(self):
      nprocs = 2
      for i in range(nprocs):
          with self.assertRaisesRegex(
              Exception,
              "\nValueError: legitimate exception from process %d$" % i,
          ):
              mp.start_processes(
                  _test_exception_single_func,
                  args=(i,),
                  nprocs=nprocs,
                  start_method=self.start_method,
              )
  
imports: import os
  import pickle
  import random
  import signal
  import sys
  import time
  import unittest
  from torch.testing._internal.common_utils import TestCase, run_tests, IS_WINDOWS, NO_MULTIPROCESSING_SPAWN
  import torch.multiprocessing
label_desc: Use image node_id 4 for calling the _TestMultiProcessing obj's underlying member method code with example usage: obj.test_exception_single() without return types