code: function (identifier, values, signs) {
              var self = this;
              return this.needByIdentifier(identifier).then(function (record) {
                  return self.addListItemsIfNotExistById(record.id, values, signs);
              });
          }
docs: Using an identifier, find document and add one or more items
  to a list of this document, the values provided specifies the list and items.
  The signs is an object list, each sign related to one or more object items in [value].
  The sign means primer key of object for determining if the object exist in list already.
  Returns a waterline (bluebird) promise with the document find and modified
  
  @param {string} identifier
  @param {Object} values {field: [value]}
  @Param {Array} signs
  @returns {Promise}