code: def test_backward_count_with_closure(torch_backward):
      """Using a closure (e.g. with LBFGS) should lead to no extra backward calls."""
  
      class TestModel(BoringModel):
          def configure_optimizers(self):
              return torch.optim.LBFGS(self.parameters(), lr=0.1)
  
      model = TestModel()
      trainer = Trainer(max_steps=5)
      trainer.fit(model)
      assert torch_backward.call_count == 5
  
      torch_backward.reset_mock()
  
      trainer = Trainer(max_steps=5, accumulate_grad_batches=2)
      trainer.fit(model)
      assert torch_backward.call_count == 10
  
file_path: pytorch-lightning/tests/tests_pytorch/trainer/optimization/test_backward_calls.py
imports: from unittest.mock import patch
  import pytest
  import torch
  from lightning.pytorch import Trainer
  from lightning.pytorch.demos.boring_classes import BoringModel
label_desc: Use image node_id 3 for calling a global function with example usage: test_backward_count_with_closure(torch_backward) and returns: torch