/**
  * Saves the tokens so that they can be used by a later incarnation of this
  * class.
  *
  * @return void
  */
 public function persistTokens()
 {
     if ($this->isPersistingRequired()) {
         $lockObject = $this->acquireLock();
         $this->updateTokens();
         $this->backendUser->setAndSaveSessionData('formTokens', $this->tokens);
         $this->resetPersistingRequiredStatus();
         $this->releaseLock($lockObject);
     }
 }