code: def test_correct_timeout_exception_msg(self):
      futures_list = [
          CANCELLED_AND_NOTIFIED_FUTURE,
          PENDING_FUTURE,
          RUNNING_FUTURE,
          SUCCESSFUL_FUTURE,
      ]
  
      with self.assertRaises(futures.TimeoutError) as cm:
          list(futures.as_completed(futures_list, timeout=0))
  
      self.assertEqual(str(cm.exception), "2 (of 4) futures unfinished")
  
file_path: cpython/Lib/test/test_concurrent_futures/test_as_completed.py
imports: import itertools
  import time
  import unittest
  import weakref
  from concurrent import futures
  from concurrent.futures._base import CANCELLED_AND_NOTIFIED, FINISHED, Future
  from test import support
  from .util import PENDING_FUTURE, RUNNING_FUTURE, CANCELLED_AND_NOTIFIED_FUTURE, EXCEPTION_FUTURE, SUCCESSFUL_FUTURE, create_future, create_executor_tests, setup_module
label_desc: Use image node_id 5 for calling the AsCompletedTests obj's underlying member method code with example usage: obj.test_correct_timeout_exception_msg() without return types