code: function(key) {
  
              // remove the item itself and its expiration time
              var ret = this._storage.removeItem(key);
              this._storage.removeItem(this._expiration_key_prefix + key);
  
              // return optional return code
              return ret;
          }
docs: Remove an item.
  @param key: Item key to remove (string).
  @return: Storage.removeItem() return code.