def METHOD_NAME(cls, info: ResolveInfo, instance):
    super().METHOD_NAME(info, instance)
    start_date = instance.start_date
    end_date = instance.end_date
    try:
        validate_end_is_after_start(start_date, end_date)
    except ValidationError as error:
        error.code = DiscountErrorCode.INVALID.value
        raise ValidationError({"end_date": error})