code: def test_arg_initializer(self):
      p = self.Pool(1, initializer=identity, initargs=(123,))
      with self.assertRaises(TypeError):
          self.Pool(initializer=123)
  
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 22 for calling the BaseTestPool obj's underlying member method code with example usage: obj.test_arg_initializer() without return types