code: def test_stretch_rgb4():
      with pytest.raises(ValueError):
          mh.stretch_rgb(np.zeros((8, 8, 3, 2)))
  
file_path: mahotas/mahotas/tests/test_stretch.py
imports: from mahotas.stretch import stretch
  import mahotas
  import mahotas
  import pytest
  import numpy
label_desc: Use image node_id 8 for calling a global function with example usage: test_stretch_rgb4() without return types