@Override
    public String toString() {
        if (source == null && variant == null) return value.toString();

        return value + " (" +
               ( source != null ? "from query profile '" + source + "'" : "") +
               ( variant != null ? " variant " + variant : "") +
                ")";
    }
Returns the variant having this value, or empty if it's not in a variant
container-search/src/main/java/com/yahoo/search/query/profile/compiled/ValueWithSource.java