code: public function getAssessmentItemRefByIdentifier(\tao_models_classes_service_StorageDirectory $privateCompilationDirectory, $identifier)
      {
          $compilationDataService = $this->getServiceLocator()->get(CompilationDataService::SERVICE_ID);
          $filename = "adaptive-assessment-item-ref-${identifier}";
          
          return $compilationDataService->readPhpCompilationData(
              $privateCompilationDirectory,
              "${filename}.php",
              "${filename}"
          );
      }
docs: Get AssessmentItemRef by Identifier
  
  This method enables you to access to a pre-compiled version of a stand alone AssessmentItemRef, that can be run
  with a stand alone AssessmentItemSession.
  
  @return \qtism\data\ExtendedAssessmentItemRef