public function getFunctions()
    {
        return [
            new \Twig_Function('begin_form',  [$this, 'beginForm']),
            new \Twig_Function('end_form',    [$this, 'endForm']),
            new \Twig_Function('form_field',  [$this, 'addFormField']),
            new \Twig_Function('text_area',   [$this, 'addTextArea']),
            new \Twig_Function('select_list', [$this, 'addSelectList']),
            new \Twig_Function('button',      [$this, 'addButton']),
            new \Twig_Function('csrf_token',  [$this, 'generateCsrfToken']),
        ];
    }