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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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]