This attachment is a patch between 2.2 in order to add latest yED compatibility, as well as colors to output.
If needed, I could write a given doc page on how to use that. Once you generate them, open yEd, load the resulting .gml file, and then Under Layout | Tree, select Layout Style as "Compact".
A workable result is here:
Note it doesn't covers some situations, so perhaps it would be interesting to add it as a new graph serializer. However, note this is inconsistent - As it needs AWT (for Font and Boundary Metrics, it might run into issues on a headless instance).