I can\'t find equivalent solution about Returning clause
DELETE FROM items WHERE sub_item_id IN %(sub_item_ids)s RETURNING item_id, sub_item_id,
To execute your query as is use Core constructs:
stmt = ItemItem.__table__.delete().\ where(ItemItem.sub_item_id.in_(sub_item_ids)).\ returning(ItemItem.item_id, ItemItem.sub_item_ids) results = session.execute(stmt).fetchall()