Get a string representing the presence of absence of relationships. Ex: P

def str_rel_short(self, goobj):
        """Get a string representing the presence of absence of relationships. Ex: P"""
        if not goobj.relationship:
            return ''
        rel_cur = goobj.relationship
        return "".join([self.rel2chr.get(r, '?') for r in self.rels if r in rel_cur])