protected function add_answer_feedback_processing(ImsQtiWriter $processing, $question)
 {
     if ($this->has_answer_feedback($question)) {
         $result = $processing->add_standard_response_assign_feedback();
         return $result;
     } else {
         return null;
     }
 }
 public function add_feedback_processing(ImsQtiWriter $processing, $question)
 {
     if ($this->has_answer_feedback($question)) {
         $response_id = $this->response_id($question);
         $feedback_id = $this->feedback_id($question);
         $result = $processing->add_standard_response_assign_feedback($response_id, $feedback_id);
         return $result;
     } else {
         return null;
     }
 }