code: def testRank(self):
      size = self.COMM.Get_size()
      rank = self.COMM.Get_rank()
      self.assertGreaterEqual(rank, 0)
      self.assertLess(rank, size)
  
imports: from mpi4py import MPI
  import mpiunittest
label_desc: Use image node_id 3 for calling the BaseTestComm obj's underlying member method code with example usage: obj.testRank() without return types