docs: function Strategy(options, setup) {
    if (typeof options == 'function') {
      setup = options;
      options = {};
    }
    
    this._codeField = options.codeField || 'code';
    this._window = options.window !== undefined ? options.window : 6;
    
    passport.Strategy.call(this);
    this._setup = setup;
    this.name = 'totp';
  }