code: def testNamed(self):
      from pickle import dumps, loads
  
      for dtype in [MPI.DATATYPE_NULL] + datatypes:
          newdtype = loads(dumps(dtype))
          self.assertIs(newdtype, dtype)
          newdtype = loads(dumps(MPI.Datatype(dtype)))
          self.assertIsNot(newdtype, dtype)
          self.assertEqual(newdtype, dtype)
  
imports: from mpi4py import MPI
  import mpiunittest
  import struct
label_desc: Use image node_id 2 for calling the TestDatatypePickle obj's underlying member method code with example usage: obj.testNamed() without return types