code: def test_multi_batch_forward_train(self):
      batch_data = self.create_batch_test_data(
          batch_shape=torch.Size([2, 3])
      )
      likelihood, labels = self.create_batch_likelihood_and_labels(
          batch_shape=torch.Size([2, 3])
      )
      model = self.create_model(batch_data, labels, likelihood)
      model.train()
      output = model(batch_data)
      self.assertTrue(output.lazy_covariance_matrix.dim() == 4)
      self.assertTrue(
          output.lazy_covariance_matrix.size(-1) == batch_data.size(-2)
      )
      self.assertTrue(
          output.lazy_covariance_matrix.size(-2) == batch_data.size(-2)
      )
  
imports: from abc import abstractmethod
  import torch
  import gpytorch
label_desc: Use image node_id 8 for calling the BaseModelTestCase obj's underlying member method code with example usage: obj.test_multi_batch_forward_train() without return types