code: def assert_pixel_by_pixel_equal(im1, im2):
      """
      Check that two PIL images are equal
      pixel-by-pixel.
      """
      # see https://stackoverflow.com/questions/1927660/compare-two-images-the-python-linux-way
      # compute pixel-by-pixel difference
      diff = PIL.ImageChops.difference(im1, im2)
      # if no difference, array is all 0's
      diffa = np.array(diff)
      assert np.count_nonzero(diffa) == 0
  
label_desc: Use image node_id 1 for calling a global function with example usage: assert_pixel_by_pixel_equal(im1, im2) without return types