public static string ToBoldText(this DocumentPart part)
        {
            Visitor visitor = new BoldTextVisitor();

            return(visitor.Visit(part));
        }
        public static string ToHTML(this DocumentPart part)
        {
            Visitor visitor = new HtmlVisitor();

            return(visitor.Visit(part));
        }
        public static string ToLaTeX(this DocumentPart part)
        {
            Visitor visitor = new LatexVisitor();

            return(visitor.Visit(part));
        }