public void Transform(Engine engine, Package package)
        {
            _log = TemplatingLogger.GetLogger(GetType());

            RepositoryLocalObject context =
                engine.GetObject(package.GetByName(Package.PageName)) as RepositoryLocalObject;
            if (context == null)
            {
                _log.Error("Could not retrieve page from package. Exiting.");
                return;
            }
            string categoryUrl = context.ContextRepository.WebDavUrl + NavigationCategoryWebDavUrl;
            Category navigation = (Category)engine.GetObject(categoryUrl);

            using (MemoryStream ms = new MemoryStream())
            {
                XmlTextWriter w = new XmlTextWriter(ms, new UTF8Encoding(false))
                {
                    Indentation = 4,
                    Formatting = Formatting.Indented
                };

                w.WriteStartDocument();
                w.WriteStartElement(Navigation.RootNodeName);
                KeywordsFilter filter = new KeywordsFilter(engine.GetSession()) { IsRoot = true };
                foreach (XmlNode rootChildren in navigation.GetListKeywords(filter))
                {
                    Keyword rootKeyword = (Keyword)engine.GetObject(rootChildren.Attributes["ID"].Value);
                    w.WriteStartElement(Navigation.NodeName);
                    NavigationNode n = new NavigationNode(rootKeyword);

                }
            }
        }