@Override
    @SuppressWarnings("unchecked")
    Iterator<Annotation> iterator(SpanNode node) {
        Collection<Annotation> annotationsForNode = spanNode2Annotation.get(node);
        if (annotationsForNode == null) {
            return Collections.<Annotation>emptyList().iterator();
        }
        return annotationsForNode.iterator();    }
TODO: Should this be removed?

@author Einar M R Rosenvinge
document/src/main/java/com/yahoo/document/annotation/SpanNode2AnnotationContainer.java