code: def add_handler(self, handler, args=None, kwargs=None):
          
          args = [] if args is None else args
          kwargs = {} if kwargs is None else kwargs
          handler_instance = handler(self, *args, **kwargs)
          if isinstance(handler_instance, RightsHandler):
              self.rights = handler_instance
          if handler_instance not in self.handlers:
              self.handlers.append(handler_instance)
docs: Registers a new handler.
  
          :param handler: handler to register.
          :type handler: :class:`fatbotslim.handlers.BaseHandler`
          :param args: positional arguments to pass to the handler's constructor.
          :type args: list
          :param kwargs: keyword arguments to pass to the handler's constructor.
          :type kwargs: dict