def _indexable_tags(self):
        """Index tag ids for tags defined in this Entity's default tags
        namespace."""
        tags = current_app.extensions.get("tags")
        if not tags or not tags.supports_taggings(self):
            return ""

        default_ns = tags.entity_default_ns(self)
        return [t for t in tags.entity_tags(self) if t.ns == default_ns]
Index tag ids for tags defined in this Entity's default tags
        namespace.