code: function (callback) {
      this.repository.getNewId(function(err, newId) {
        if (err) {
          debug(err);
          return callback(err);
        }
        callback(null, newId);
      });
    }
docs: Use this function to obtain a new id.
  @param {Function} callback The function, that will be called when the this action is completed.
  `function(err, id){}` id is of type String.