code: def _test_call(self, op, args, res):
      self.assertEqual(op(*args), res)
      self.assertEqual(MPI.Op(op)(*args), res)
  
imports: from mpi4py import MPI
  import mpiunittest
label_desc: Use image node_id 4 for calling the TestOp obj's underlying member method code with example usage: obj._test_call(op, args, res) without return types