code: def test_ddp_post_local_sgd_comm_hook(tmpdir):
      """Test for DDP post-localSGD hook."""
      model = BoringModel()
      strategy = TestDDPStrategy(
          expected_ddp_comm_hook_name=post_localSGD.post_localSGD_hook.__qualname__,
          ddp_comm_state=post_localSGD.PostLocalSGDState(
              process_group=None,
              subgroup=None,
              start_localSGD_iter=8,
          ),
          ddp_comm_hook=post_localSGD.post_localSGD_hook,
          model_averaging_period=4,
      )
      trainer = Trainer(
          fast_dev_run=True,
          accelerator="gpu",
          devices=2,
          strategy=strategy,
          default_root_dir=tmpdir,
          sync_batchnorm=True,
          enable_progress_bar=False,
          enable_model_summary=False,
      )
      trainer.fit(model)
      assert (
          trainer.state.finished
      ), f"Training failed with {trainer.state}"
  
file_path: pytorch-lightning/tests/tests_pytorch/strategies/test_ddp_integration_comm_hook.py
imports: from unittest import mock
  import pytest
  import torch
  from lightning.pytorch import Trainer
  from lightning.pytorch.demos.boring_classes import BoringModel
  from lightning.pytorch.strategies import DDPStrategy
  from tests_pytorch.helpers.runif import RunIf
label_desc: Use image node_id 5 for calling a global function with example usage: test_ddp_post_local_sgd_comm_hook(tmpdir) without return types