code: def push(img):
      """Push an image onto the shared image stack.
  
      Parameters
      ----------
      img : ndarray
          Image to push.
  
      """
      if not isinstance(img, np.ndarray):
          raise ValueError("Can only push ndarrays to the image stack.")
  
      image_stack.append(img)
  
label_desc: Use image node_id 1 for calling a global function with example usage: push(img) without return types