@Override
    public FixedWidthFunction copy() {
        return new FixedWidthFunction(getLabel(), getLevelOrNull(), getArg(0).copy(), (ConstantValue)getArg(1).copy());
    }
Constructs a new instance of this class.

@param exp        The expression to evaluate.
@param width The width of each bucket.
container-search/src/main/java/com/yahoo/search/grouping/request/FixedWidthFunction.java