code: public function createService(ServiceLocatorInterface $serviceLocator)
      {
          if ($serviceLocator instanceof ServiceLocatorAwareInterface) {
              $serviceLocator = $serviceLocator->getServiceLocator();
          }
  
          $form = $this->buildForm($serviceLocator);
  
          $config = $serviceLocator->get('Config');
          if (isset($config['captcha'])) {
              $form->add($config['captcha']);
          }
  
          $this->addCsrfTo($form);
          $this->addSubmitTo($form);
  
          return $form;
      }
docs: {@inheritdoc}
  @return FormInterface