public boolean removeItem(Item item) {
        int removedIndex = getItemIndex(item);
        boolean removed = super.removeItem(item);

        if (removed && removedIndex == 0) {
            insertTrueFirstItem();
        }
        return removed;
    }
Convenience method for adding a positive item.
If a positive item is already present
the positive item becomes an AndItem with the items added
container-search/src/main/java/com/yahoo/prelude/query/NotItem.java