code: def test_lut(op):
      lb = ImageMorph.LutBuilder(op_name=op)
      assert lb.get_lut() is None
  
      lut = lb.build_lut()
      with open(f"Tests/images/{op}.lut", "rb") as f:
          assert lut == bytearray(f.read())
  
imports: from __future__ import annotations
  import pytest
  from PIL import Image, ImageMorph, _imagingmorph
  from .helper import assert_image_equal_tofile, hopper
label_desc: Use image node_id 6 for calling a global function with example usage: test_lut(op) without return types