@Override
    public Iterator<Json> iterator() {
        requireType(ARRAY);
        return new Iterator<>() {
            private int current = 0;
            @Override public boolean hasNext() { return current < length(); }
            @Override public Json next() { return entry(current++); }
        };
    }
@return true if the JSON field was present but its value was 'null'
vespajlib/src/main/java/ai/vespa/json/Json.java