def METHOD_NAME(api_client, event, registration):
    reservation = SeatReservationCode.objects.create(seats=1, registration=registration)
    reservation_data = {
        "seats": 1,
        "registration": registration.id,
    }
    response = update_seats_reservation(api_client, reservation.id, reservation_data)
    assert response.status_code == status.HTTP_400_BAD_REQUEST
    assert response.data["code"][0].code == "required"