code: function handle(router, method, file) {
    if (method && typeof method === 'object') return router.all(method);
    if (!router.routes.has(method)) {
      throw new Error(`Router handler "${method}" does not exist`);
    }
    for (let route of router.routes.get(method)) route.handle(file);
    return file;
  }
docs: Sync methods