docs: function(key, value) {
        var string_value = (typeof value == 'string') ? value : JSON.stringify(value);
        key = key.toString();
        this.storage.set(key, string_value);
        if (key != this.meta_key) {
          this._addKey(key);
          this.$element.trigger('set-' + this.name, {key: key, value: value});
          this.$element.trigger('set-' + this.name + '-' + key, {key: key, value: value});
        };
        // always return the original value
        return value;
      }