public function getTocs()
    {
        $tocs = array();

        $nodes = $this->getNodes(function($node) {
            return $node instanceof TocNode;
        });

        foreach ($nodes as $toc) {
            $files = $toc->getFiles();

            foreach ($files as &$file) {
                $file = $this->environment->canonicalUrl($file);
            }

            $tocs[] = $files;
        }

        return $tocs;
    }