Fill go2obj with all relationship key GO IDs and their objects.

def fill_relationshiprevgo2obj(self, goobj):
        """Fill go2obj with all relationship key GO IDs and their objects."""
        for reltyp, relgoobjs in goobj.relationship_rev.items():
            if reltyp in self.relationships:
                for relgoobj in relgoobjs:
                    if relgoobj.id not in self.go2obj:
                        self.go2obj[relgoobj.id] = relgoobj
                        self.fill_relationshiprevgo2obj(relgoobj)