Return source GO IDs .

def get_usrgos(self, fin_goids, prt):
        """Return source GO IDs ."""
        ret = self.get_goids(None, fin_goids, prt)
        # If there have been no GO IDs explicitly specified by the user
        if not ret:
            # If the GO-DAG is sufficiently small, print all GO IDs
            if self.max_gos is not None and len(self.go2obj) < self.max_gos:
                main_gos = set(o.id for go, o in self.go2obj.items() if go != o.id)
                go_leafs = set(go for go, o in self.go2obj.items() if not o.children)
                ret = go_leafs.difference(main_gos)
            else:
                raise RuntimeError("GO IDs NEEDED")
        go2obj = self.get_go2obj(ret)
        return get_go2obj_unique(go2obj)