code: def test_should_save_grayscale_image(output_dir):
      input_image = np.ones((28, 28, 1), dtype="uint8")
  
      save_grayscale(input_image, output_dir, "grayscale.png")
  
      assert len(list(Path(output_dir).iterdir())) == 1
  
imports: from pathlib import Path
  import numpy
  from tf_explain.utils.saver import save_grayscale, save_rgb
label_desc: Use image node_id 1 for calling a global function with example usage: test_should_save_grayscale_image(output_dir) without return types