code: def test_dxt5_colorblock_alpha_issue_4142():
      """Check that colorblocks are decoded correctly in DXT5"""
  
      with Image.open(
          "Tests/images/dxt5-colorblock-alpha-issue-4142.dds"
      ) as im:
          px = im.getpixel((0, 0))
          assert px[0] != 0
          assert px[1] != 0
          assert px[2] != 0
  
          px = im.getpixel((1, 0))
          assert px[0] != 0
          assert px[1] != 0
          assert px[2] != 0
  
imports: from io import BytesIO
  import pytest
  from PIL import DdsImagePlugin, Image
  from .helper import assert_image_equal, assert_image_equal_tofile, hopper
label_desc: Use image node_id 15 for calling a global function with example usage: test_dxt5_colorblock_alpha_issue_4142() without return types