foo.py

    @classmethod
    def group_key(cls, box_shipment: NamedTuple) -> str:
        return ",".join(
            [
                str(box_shipment.club_id),
                str(box_shipment.theme_id),
                ",".join(sorted([str(book_id) for book_id in box_shipment.book_ids])),
                str(box_shipment.outgoing_label),
                str(box_shipment.sent),
                str(box_shipment.box_weight_oz),
                str(box_shipment.inserts_weight_oz),
                str(box_shipment.return_mailer_weight_oz),
                str(box_shipment.id)
                if box_shipment.shipping_address_validation_error
                else "",
            ]
        )