code: def testAll1(self):
      ctx = GReqCtx()
      greq = MPI.Grequest.Start(ctx.query, None, None)
      self.assertFalse(greq.Test())
      greq.Cancel()
      greq.Complete()
      status = MPI.Status()
      self.assertTrue(greq.Test(status))
      self.assertEqual(status.Get_source(), ctx.source)
      self.assertEqual(status.Get_tag(), ctx.tag)
      self.assertEqual(status.Get_error(), MPI.SUCCESS)
      self.assertFalse(status.Is_cancelled())
      greq.Wait()
  
file_path: mpi4py/test/test_grequest.py
imports: from mpi4py import MPI
  import mpiunittest
label_desc: Use image node_id 4 for calling the TestGrequest obj's underlying member method code with example usage: obj.testAll1() without return types