@Override
    public SpanNode next() {
        SpanNode retval = null;
        try {
            retval = base.next();
        } finally {
            returnedFromNext = retval;
        }
        return returnedFromNext;
    }
@author <a href="mailto:einarmr@yahoo-inc.com">Einar M R Rosenvinge</a>
document/src/main/java/com/yahoo/document/annotation/InvalidatingIterator.java