code: def test_test_step(self, trainer, batch):
      # Test testing step.
      trainer.test_step(batch, batch_idx=0)
  
imports: import pytest
  import torch
  import torch.nn
  from torch.utils.data import DataLoader, TensorDataset
  from kale.embed.image_cnn import SimpleCNNBuilder
  from kale.pipeline.base_nn_trainer import BaseNNTrainer, CNNTransformerTrainer, MultimodalNNTrainer
  from kale.predict.class_domain_nets import ClassNet
label_desc: Use image node_id 8 for calling the TestCNNTransformerTrainer obj's underlying member method code with example usage: obj.test_test_step(trainer, batch) without return types