code: def test_rgb2grey():
      f = luispedro_jpg()
      fg = rgb2grey(f)
      fg8 = rgb2grey(f, dtype=np.uint8)
      assert f.ndim == 3
      assert fg.ndim == 2
      assert fg8.ndim == 2
      assert fg.shape[0] == f.shape[0]
      assert fg.shape[1] == f.shape[1]
      assert fg.shape == fg8.shape
      assert fg8.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 2 for calling a global function with example usage: test_rgb2grey() without return types