Get all parents/relationships on this GOTerm.

def _getobjs_higher(self, idobj):
        """Get all parents/relationships on this GOTerm."""
        idobjs_higher = set(idobj.parents)
        for reltyp, relidobjs in idobj.relationship.items():
            if self.relationships is True or reltyp in self.relationships:
                idobjs_higher.update(relidobjs)
        return idobjs_higher