public boolean hasSpanNode() {
        return spanNode != null;
    }
Returns true if this Annotation is associated with a SpanNode (irrespective of the SpanNode being valid or not).

@return true if this Annotation is associated with a SpanNode, false otherwise.
@see com.yahoo.document.annotation.SpanNode#isValid()
document/src/main/java/com/yahoo/document/annotation/Annotation.java