code: function() {
      var obj = {};
      for (var type in this.prefs_) {
        if (this.prefs_.hasOwnProperty(type)) {
          obj[type] = this.prefs_[type].name;
        }
      }
      return obj;
    }
docs: Converts this instance to its JSON representation.
  @return {!Object.<string, string>} The JSON representation of this set of
  preferences.