code: function proxy (original, routes) {
    return new Proxy(original, {
      get(target, key, receiver) {
        const method = target[key]
        if (method) return method
        else return function (path, ...args) {
          const cb = args[0]
          if (typeof cb === 'function') {
            original.add(key, path, cb)
          } else {
            const fn = routes[key]
            return fn && fn.exec(path, ...args)
          }
        }
      }
    })
  }
docs: Proxy function with router.
  
  @param {Function} original
  @param {Object} routes
  @api private