code: def test_warning_if_mps_not_used(mps_count_1):
      with pytest.warns(
          UserWarning, match="GPU available but not used"
      ):
          Trainer(accelerator="cpu")
  
file_path: pytorch-lightning/tests/tests_pytorch/accelerators/test_mps.py
imports: from collections import namedtuple
  import pytest
  import torch
  from lightning.pytorch import Trainer
  from lightning.pytorch.accelerators import MPSAccelerator
  from lightning.pytorch.demos.boring_classes import BoringModel
  import tests_pytorch.helpers.pipelines
  from tests_pytorch.helpers.runif import RunIf
label_desc: Use image node_id 3 for calling a global function with example usage: test_warning_if_mps_not_used(mps_count_1) without return types