code: def testConstructorCartcomm(self):
      comm = MPI.COMM_SELF
      cart = comm.Create_cart([1])
      with self.assertRaises(TypeError):
          MPI.Graphcomm(cart)
      with self.assertRaises(TypeError):
          MPI.Distgraphcomm(cart)
      cart.Free()
  
imports: from mpi4py import MPI
  import mpiunittest
label_desc: Use image node_id 2 for calling the TestTopoConstructor obj's underlying member method code with example usage: obj.testConstructorCartcomm() without return types