Write hierarchy below specfied GO IDs.

def prt_hier(self, prt=sys.stdout):
        """Write hierarchy below specfied GO IDs."""
        objwr = WrHierGO(self.gosubdag, **self.kws)
        assert self.goids, "NO VALID GO IDs WERE PROVIDED"
        if 'up' not in objwr.usrset:
            for goid in self.goids:
                objwr.prt_hier_down(goid, prt)
        else:
            objwr.prt_hier_up(self.goids, prt)