code: def test_alpha():
      # Issue https://github.com/python-pillow/Pillow/issues/899
      # Is alpha preserved through image enhancement?
  
      original = _half_transparent_image()
  
      for op in ["Color", "Brightness", "Contrast", "Sharpness"]:
          for amount in [0, 0.5, 1.0]:
              _check_alpha(
                  getattr(ImageEnhance, op)(original).enhance(amount),
                  original,
                  op,
                  amount,
              )
  
imports: from PIL import Image, ImageEnhance
  from .helper import assert_image_equal, hopper
label_desc: Use image node_id 5 for calling a global function with example usage: test_alpha() without return types