code: def test_multi_batch_backward_train(
      self, batch_shape=torch.Size([2, 3])
  ):
      return self.test_batch_backward_train(batch_shape=batch_shape)
  
imports: from abc import abstractmethod
  import torch
  import gpytorch
label_desc: Use image node_id 3 for calling the VariationalModelTestCase obj's underlying member method code with example usage: obj.test_multi_batch_backward_train(batch_shape) and returns: self