@Override
    public WordAlternativesItem clone() {
        var clone = (WordAlternativesItem)super.clone();
        clone.alternatives = new ArrayList(this.alternatives);
        return clone;
    }
Add a new alternative iff the term string is not already present with an
equal or higher exactness score. If the term string is present with a
lower exactness score, the new, higher score will take precedence.

@param term one of several string interpretations of the input word
@param exactness how close the term string matches what the user input
container-search/src/main/java/com/yahoo/prelude/query/WordAlternativesItem.java