public ITagger <T> CreateTagger <T>(ITextBuffer buffer) where T : ITag
        {
            IOutliningManager manager = UserOutliningManager.GetManager(buffer);

            if (typeof(T) == typeof(IOutliningRegionTag))
            {
                return(manager.GetOutliningTagger() as ITagger <T>);
            }
            return(manager.GetGlyphTagger() as ITagger <T>);
        }