code: function(key, data, callback) {
        if (key) {
          if (data) {
            var _data = data;
            if ('undefined' !== typeof window && 'object' === typeof data) {
              _data = JSON.stringify(_data);
            }
            this.store.proxy.set(this.prefix + key, _data);
            callback(null);
          } else {
            callback('missing data');
          }
        } else {
          callback('missing key');
        }
      }
docs: Save an item
  
  @param {String} key The key of the item
  @param {Object} data The item
  @param {Function} callback Function called when the session is saved
  @return {callback(err)} The callback to execute as result
  @param {String} callback.status Result from Redis query