code: function (identifier, values) {
              var self = this;
              return this.needByIdentifier(identifier).then(function (record) {
                  return self.removeListItemsById(record.id, values);
              });
          }
docs: Using an identifier, find document and delete one or more items
  from a list of this document, the values provided specifies the list and items.
  Returns a waterline (bluebird) promise with the document find and modify
  
  @param {string} identifier
  @param {Object} values {field: [value]}
  @returns {Promise}