void appendContentsString(StringBuilder buffer) {
        buffer.append("'");
        for (Iterator<Item> i = getItemIterator(); i.hasNext();) {
            WordItem wordItem = (WordItem) i.next();

            buffer.append(wordItem.getWord());
            if (i.hasNext()) {
                buffer.append(" ");
            }
        }
        buffer.append("'");
    }
Segment phrase items uses a empty heading instead of "SPHRASE "
container-search/src/main/java/com/yahoo/prelude/query/PhraseSegmentItem.java