Method addRelations

/**
 * Allows the user to add names of properties that will be interpreted as relations
 * Note that if there is an existing data property it will also be displayed as well
 * as the relation due to the internal implementation (this behaviour is not part of this API
 * however and should not be guaranteed)
 *
 * @param   string[]  $fields  The array of additional fields to add as relations
 *
 * @return  void
 */
public function addRelations(array $fields) : void
{
    $this->extraRelations = array_merge($this->extraRelations, $fields);
}