what is the gfa input for collapse.bash

[adf-ncgr]

this script takes a single gfa file but then passes it to serve as both genefamiliesa and genefamiliesb when it calls collapse_overlapping.py.
That seems a bit confusing, is it supposed to be a concatenated gfa file? If so, wouldn't it make more sense to just let collapse.bash take two separate gfas as arguments and pass them along separately? Seems likely that the logic for collapse_self.bash got introduced here unintentionally.