code: def test_format_change_warning(tmp_path):
      img = np.full((100, 100, 3), 42, dtype=np.uint8)
  
      with iio.imopen(
          tmp_path / "test.gif", "w", plugin="pillow"
      ) as file:
          file.write(img, format="PNG")
  
          with pytest.warns(UserWarning):
              file.write(img, format="GIF")
  
imports: import io
  import os
  from pathlib import Path
  import imageio.v3
  import numpy
  import pytest
  from imageio.core.request import InitializationError, Request
  from imageio.core.v3_plugin_api import PluginV3
  from imageio.plugins.pillow import PillowPlugin
  from PIL import Image, ImageSequence, ImageOps, __version__
label_desc: Use image node_id 42 for calling a global function with example usage: test_format_change_warning(tmp_path) without return types