code: def test_1px_width(tmp_path):
      im = Image.new("L", (1, 256))
      px = im.load()
      for y in range(256):
          px[0, y] = y
      _roundtrip(tmp_path, im)
  
file_path: pillow/Tests/test_file_pcx.py
imports: from __future__ import annotations
  import pytest
  from PIL import Image, ImageFile, PcxImagePlugin
  from .helper import assert_image_equal, hopper
label_desc: Use image node_id 7 for calling a global function with example usage: test_1px_width(tmp_path) without return types