Returns the relative path (from the images directory) to the original file
    used when construction the sprite. This is suitable for passing to the
    image_width and image_height helpers.

def _sprite_file(map, sprite):
    """
    Returns the relative path (from the images directory) to the original file
    used when construction the sprite. This is suitable for passing to the
    image_width and image_height helpers.
    """
    map = StringValue(map).value
    sprite_name = StringValue(sprite).value
    sprite_map = sprite_maps.get(map)
    sprite = sprite_map and sprite_map.get(sprite_name)
    if not sprite_map:
        log.error("No sprite map found: %s", map)
    elif not sprite:
        log.error("No sprite found: %s in %s", sprite_name, sprite_map['*n*'])
    if sprite:
        return QuotedStringValue(sprite[1][0])
    return StringValue(None)