@Override
        boolean serialize(StringBuilder destination, PredicateQueryItem item) {
            destination.append("predicate(").append(item.getIndexName()).append(',');
            appendFeatures(destination, item.getFeatures());
            destination.append(',');
            appendFeatures(destination, item.getRangeFeatures());
            destination.append(')');
            return false;
        }
Serialize Vespa query trees to YQL+ strings.

@author Steinar Knutsen
container-search/src/main/java/com/yahoo/search/yql/VespaSerializer.java