def METHOD_NAME(self):
    """
    Returns:
        int: Formation index.
    """
    image = self.image_crop(MAP_BUFF)
    if TEMPLATE_FORMATION_2.match(image):
        buff = 'double_line'
    elif TEMPLATE_FORMATION_1.match(image):
        buff = 'line_ahead'
    elif TEMPLATE_FORMATION_3.match(image):
        buff = 'diamond'
    else:
        buff = 'unknown'
    logger.attr('Map_buff', buff)
    return buff