code: def update():
      global data, curves, img, ptr, imgLevels
      ptr = (ptr + 1) % data.shape[0]
      data[ptr]
      img.setImage(data[ptr], levels=imgLevels)
      for c in curves:
          c.setData(data[ptr])
  
label_desc: Use image node_id 1 for calling a global function with example usage: update() without return types