/**
  * Returns singleton instance of this class
  *
  * @return Tx_PtExtbase_Tree_TreeRepositoryBuilder
  */
 public static function getInstance()
 {
     if (self::$instance === null) {
         $objectManager = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('TYPO3\\CMS\\Extbase\\Object\\ObjectManager');
         self::$instance = $objectManager->get('Tx_PtExtbase_Tree_TreeRepositoryBuilder');
     }
     return self::$instance;
 }