code: def test_training_iteration(
      self,
      data_batch_shape=None,
      inducing_batch_shape=None,
      model_batch_shape=None,
      expected_batch_shape=None,
      constant_mean=True,
  ):
      # We cannot inheret the superclass method
      # Because it expects `variational_params_intialized` to be set to 0
  
      # Batch shapes
      model_batch_shape = (
          model_batch_shape
          if model_batch_shape is not None
          else self.batch_shape
      )
      data_batch_shape = (
          data_batch_shape
          if data_batch_shape is not None
          else self.batch_shape
      )
      inducing_batch_shape = (
          inducing_batch_shape
          if inducing_batch_shape is not None
          else self.batch_shape
      )
      expected_batch_shape = (
          expected_batch_shape
          if expected_batch_shape is not None
          else self.batch_shape
      )
  
      # Make model and likelihood
      model, likelihood = self._make_model_and_likelihood(
          batch_shape=model_batch_shape,
          inducing_batch_shape=inducing_batch_shape,
          distribution_cls=self.distribution_cls,
          strategy_cls=self.strategy_cls,
          constant_mean=constant_mean,
      )
  
      # Do forward pass
      # Iter 1
      self._training_iter(
          model,
          likelihood,
          data_batch_shape,
          mll_cls=self.mll_cls,
          cuda=self.cuda,
      )
      # Iter 2
      output, loss = self._training_iter(
          model,
          likelihood,
          data_batch_shape,
          mll_cls=self.mll_cls,
          cuda=self.cuda,
      )
      self.assertEqual(output.batch_shape, expected_batch_shape)
      self.assertEqual(output.event_shape, self.event_shape)
      self.assertEqual(loss.shape, expected_batch_shape)
  
imports: import unittest
  import torch
  import gpytorch
  from gpytorch.test.variational_test_case import VariationalTestCase
label_desc: Use image node_id 10 for calling the TestVNNGP obj's underlying member method code with example usage: obj.test_training_iteration(data_batch_shape, inducing_batch_shape, model_batch_shape, expected_batch_shape, constant_mean) without return types