Want to use VTD-XML to extract inner Xml: Guess this is what VTDNav.getContentFragment is for. How does is work?

Question

I am trying to figure out how I could extract an inner Xml String from a Xml document. According to the API there a method VTDNav.getContentFragment() which seems to be the right choice. But this method returns a long. How do I use that long value to retrieve the xml between the two tags? Any help appreciated. Thanks in advance.