public function getFilters()
    {
        return array(
            'markdown' => new Twig_SimpleFilter('markdown', array($this, 'markdownFilter')),
            'map' => new Twig_SimpleFilter('map', array($this, 'mapFilter')),
            'sort_by' => new Twig_SimpleFilter('sort_by', array($this, 'sortByFilter')),
            'link' => new Twig_SimpleFilter('link', array($this->pico, 'getPageUrl'))
        );
    }