def scroll(get_frame, t):
    """
    This function returns a 'region' of the current frame.
    The position of this region depends on the time.
    """
    frame = get_frame(t)
    frame_region = frame[int(t) : int(t) + 360, :]
    return frame_region

    This function returns a 'region' of the current frame.
    The position of this region depends on the time.
    
docs/_static/code/user_guide/effects/transform.py