question: How to test in low version
context: There is no train.test () in the lower version. How to test the test data set?
  my version: 0.4.6
answer: Hi
  PyTorch Lightning 0.4.6 is extremely old. You should consider upgrading.
  That being said, you can always test your model as you would in plain pytorch, because the LightningModule is also just a nn.Module:
  for inp, target in test_dataloader:
      pred = model(inp)
      test_loss = loss(pred, target)
      ...