code: def test_warning_if_gpus_not_used(cuda_count_1):
      with pytest.warns(
          UserWarning, match="GPU available but not used"
      ):
          Trainer(accelerator="cpu")
  
file_path: pytorch-lightning/tests/tests_pytorch/accelerators/test_gpu.py
imports: from unittest import mock
  import pytest
  import torch
  from lightning.pytorch import Trainer
  from lightning.pytorch.accelerators import CUDAAccelerator
  from lightning.pytorch.accelerators.cuda import get_nvidia_gpu_stats
  from lightning.pytorch.demos.boring_classes import BoringModel
  from tests_pytorch.helpers.runif import RunIf
label_desc: Use image node_id 5 for calling a global function with example usage: test_warning_if_gpus_not_used(cuda_count_1) without return types