Thanks Tiago for a quick reply. I think I will write the generation part in C++/Fortran and save the graph-data, say in the form of an edge list, in a file which can then be processed using graph-tool. However, I really appreciate your idea of writing a documentation for explaining the writings of extensions for graph-tool.
On a side note, since your generalized communities model also needs different probability value for each pair, I would guess that for generation of such graphs, you have written a code in C++ and that has not been included in graph-tool. Is there a plan to include the same in the graph-tool sometime in near future?