public function __construct()
{
parent::__construct();
// Initialize helper manager
$this->_helperManager = new \Zend\View\HelperPluginManager();
$this->_helperManager->setRenderer($this);
// Inject form-related invokable helpers
$helperConfig = new \Zend\Form\View\HelperConfig();
$helperConfig->configureServiceManager($this->_helperManager);
}