<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def cleanup_relations(self):
 """Cleanup listing relations"""

        collections = self.collections
        for relation in [x for col in collections.values()
                         for x in col.model.relations.values()]:
            db.session.query(relation)\
                       .filter(~relation.listing.any())\
                       .delete(synchronize_session=False)
        db.session.commit()