I am able to use LEDA C++ library. For some applications and for some comparisons, I need to convert graphs from LEDA to Grapviz format. I am working on it, and I will post the LEDA source code later.
I worked on the topic related with Directed Layered Graphs. I think that it would be useful to see existing graphs of LEDA in graphviz.
Here is preliminary showcase of the work