code: protected function getItemRef($itemIdentifier)
      {
          $serviceContext = $this->getServiceContext();
          /** @var QtiRunnerMap $mapService */
          $mapService = $this->getServiceLocator()->get(QtiRunnerMap::SERVICE_ID);
          return $mapService->getItemHref($serviceContext, $itemIdentifier);
      }
docs: Gets the item reference for the current itemRef
  
  @param string $itemIdentifier the item id
  @return string the state id