code: def test_training_step(multimodal_model):
      x = [torch.rand(1, 5) for _ in range(2)]
      y = torch.tensor([1])
      batch = [*x, y]
      loss = multimodal_model.training_step(batch, 0)
      assert isinstance(loss, torch.Tensor)
  
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 6 for calling a global function with example usage: test_training_step(multimodal_model) without return types