code: def testGroup(self):
      comm = self.COMM
      group = self.COMM.Get_group()
      self.assertEqual(comm.Get_size(), group.Get_size())
      self.assertEqual(comm.Get_rank(), group.Get_rank())
      group.Free()
      self.assertEqual(group, MPI.GROUP_NULL)
  
imports: from mpi4py import MPI
  import mpiunittest
label_desc: Use image node_id 4 for calling the BaseTestComm obj's underlying member method code with example usage: obj.testGroup() without return types