* @param extractData the extract data to populate
     */
    protected void extractFrontMatterMetadata(final Node document, final ExtractData extractData) {
        final YamlFrontMatterVisitor visitor = new YamlFrontMatterVisitor();
        document.accept(visitor);

        final Map<String, List<String>> frontMatter = visitor.getData();
        for (final Map.Entry<String, List<String>> entry : frontMatter.entrySet()) {