Write hierarchy for all GO IDs below GO ID in arg, goid.

def prt_hier_down(self, goid, prt=sys.stdout):
        """Write hierarchy for all GO IDs below GO ID in arg, goid."""
        wrhiercfg = self._get_wrhiercfg()
        obj = WrHierPrt(self.gosubdag.go2obj, self.gosubdag.go2nt, wrhiercfg, prt)
        obj.prt_hier_rec(goid)
        return obj.items_list