@Override
    public StringBucket copy() {
        return new StringBucket(getLabel(), getLevelOrNull(), getFrom().copy(), getTo().copy());
    }
Constructs a new bucket for a range of strings.

@param from the start of the bucket, inclusive
@param to the end of the bucket, exclusive
container-search/src/main/java/com/yahoo/search/grouping/request/StringBucket.java