public OrderSpecifier<T> desc() {
        if (desc == null) {
            desc = new OrderSpecifier<T>(Order.DESC, mixin);
        }
        return desc;
    }
Create an OrderSpecifier for descending order of this expression

@return descending order by this
querydsl-core/src/main/java/com/querydsl/core/types/dsl/ComparableExpressionBase.java