[graph-tool] getting the hierarchy tree

Hi again, How is it possible to return the hierarchy tree from a NestedBlockModel? I've found that the gt.get_hierarchy_tree returns the tree as graph, but I couldn't understand how to map partition names at each level n to the ones at level n+1. Actually I'm doing this iteratively running state.project_partition() and using crosstabs to do the matches, but I wonder if there's a smarter way to proceed. Cheers, d