code: def test_colors():
      f = luispedro_jpg()
      lab = rgb2lab(f)
      assert np.max(np.abs(lab)) <= 100.0
      assert np.max(np.abs(xyz2rgb(rgb2xyz(f)) - f)) < 1.0
  
      lab8 = rgb2lab(f, dtype=np.uint8)
      assert lab.dtype != np.uint8
      assert lab8.dtype == np.uint8
  
      xyz = rgb2xyz(f, dtype=np.uint8)
      assert xyz.shape == f.shape
      assert xyz.dtype == np.uint8
  
imports: import mahotas
  import numpy
  from mahotas.tests.utils import luispedro_jpg
  from mahotas.colors import rgb2xyz, rgb2lab, xyz2rgb, rgb2grey, rgb2sepia
label_desc: Use image node_id 1 for calling a global function with example usage: test_colors() without return types