docs: def url(pattern, order = 0):
      """
          Class Decorator: 设置路径匹配模式和排序序号
  
          1. 支持设置多个链接匹配规则。
  
          参数:
              pattern     链接正则匹配
              order       排序序号
  
          示例:
              @url(r"(?i)/(index.html?)?", 10)
              @url(r"(?i)/default.html?", 8)
              class IndexHandler(BaseHandler):
                  pass
      """
      def actual(handler):
          if not isclass(handler) or not issubclass(handler, BaseHandler):
              raise Exception("must be BaseHandler's sub class.")
  
          if not hasattr(handler, "__urls__"): handler.__urls__ = []
          handler.__urls__.append((pattern, order))
  
          return handler
  
      return actual