code: def testPickle(self):
      from pickle import dumps, loads
  
      comm_null = loads(dumps(MPI.COMM_NULL))
      self.assertIs(comm_null, MPI.COMM_NULL)
      comm_null = loads(dumps(MPI.Comm(MPI.COMM_NULL)))
      self.assertIsNot(comm_null, MPI.COMM_NULL)
      self.assertEqual(comm_null, MPI.COMM_NULL)
  
imports: from mpi4py import MPI
  import mpiunittest
label_desc: Use image node_id 5 for calling the TestCommNull obj's underlying member method code with example usage: obj.testPickle() without return types