code: def test_write_bytes(test_images):
      img = iio.imread(
          test_images / "cockatoo.mp4",
          plugin="pyav",
          filter_sequence=[
              ("framestep", "5"),
              ("scale", {"size": "vga", "flags": "lanczos"}),
          ],
      )
      img_bytes = iio.imwrite(
          "<bytes>",
          img,
          extension=".mp4",
          plugin="pyav",
          codec="libx264",
      )
  
      assert img_bytes is not None
  
imports: import io
  import warnings
  from contextlib import ExitStack
  from pathlib import Path
  import numpy
  import pytest
  from conftest import IS_PYPY
  import imageio.v3
  from av.video.format import names
  from imageio.plugins.pyav import _format_to_dtype
label_desc: Use image node_id 9 for calling a global function with example usage: test_write_bytes(test_images) without return types