@Override
    public DayOfWeekFunction copy() {
        return new DayOfWeekFunction(getLabel(), getLevelOrNull(), getArg(0).copy());
    }
Constructs a new instance of this class.

@param exp The expression to evaluate, must evaluate to a long.
container-search/src/main/java/com/yahoo/search/grouping/request/DayOfWeekFunction.java