code: def test_enter_exit(self):
      pool = self.Pool(1)
  
      with pool:
          pass
      # with self.assertRaises(ValueError):
      #     with pool:
      #         pass
  
      pool.join()
  
imports: from mpi4py import MPI
  import mpi4py.util.pool
  import concurrent.futures
  import itertools
  import functools
  import warnings
  import unittest
  import time
  import sys
  import os
label_desc: Use image node_id 18 for calling the BaseTestPool obj's underlying member method code with example usage: obj.test_enter_exit() without return types