In the OrgCharter sample application of version 2.3 (GoWin and GoWeb) we have included an example of the use of GraphML.
Alas, there cannot be any single standard design (or implementation) for how to map GoDocuments and GoObjects to GraphML elements and attributes. The classes that we provide are more general than are needed for just the OrgCharter sample, but they are also not specific or thorough enough for many other kinds of applications. If you are serious about using GraphML, you will need to spend time understanding this code before you can adapt it.