def retrieve(self, tagname, monthyear): query = Tag.query(Tag.monthyear == monthyear, ancestor=Tag.get_tag_parent_key(tagname)) tagmodels = query.fetch(1) if len(tagmodels) == 0: tag = Tag(parent=Tag.get_tag_parent_key(tagname)) tag.name = tagname tag.monthyear = monthyear else: tag = tagmodels[0] return tag