code: def test_f_lut():
      """Tests for floating point lut of 8bit gray image"""
      im = hopper("L")
      lut = [0.5 * float(x) for x in range(256)]
  
      out = im.point(lut, "F")
  
      int_lut = [x // 2 for x in range(256)]
      assert_image_equal(out.convert("L"), im.point(int_lut, "L"))
  
imports: import pytest
  from .helper import assert_image_equal, hopper
label_desc: Use image node_id 3 for calling a global function with example usage: test_f_lut() without return types