public function onTwigRegistered(&$twig)
    {
        // If a theme is not found, it will be searched for in PicoAuth/theme
        $twig->getLoader()->addPath($this->pluginDir . '/theme');

        $this_instance = $this;
        $twig->addFunction(
            new \Twig_SimpleFunction(
                'csrf_token',
                function ($action = null) use (&$this_instance) {
                    return $this_instance->csrf->getToken($action);
                },
                array('is_safe' => array('html'))
            )
        );
        $twig->addFunction(
            new \Twig_SimpleFunction(
                'csrf_field',
                function ($action = null) use (&$this_instance) {
                    return '<input type="hidden" name="csrf_token" value="'
                        . $this_instance->csrf->getToken($action)
                        . '">';
                },
                array('is_safe' => array('html'))
            )
        );
    }