code: public function isValid()
      {
          $isValid = parent::isValid();
          if ($isValid) {
              $this->setRenderMode(self::RENDER_SUMMARY);
          }
          
          return $isValid;
      }
docs: {@inheritDoc}
  
  Sets render mode to {@link RENDER_SUMMARY}, if validation succeeded.
  
  @see \Zend\Form\Form::isValid()