private Item advancedItems(boolean topLevel) {
        int position = tokens.getPosition();
        Item item = null;

        try {
            item = advancedItemsBody(topLevel);
            return item;
        } finally {
            if (item == null) {
                tokens.setPosition(position);
            }
        }
    }
A collection of one or more advanced items.
container-search/src/main/java/com/yahoo/prelude/query/parser/AdvancedParser.java