@Override
    public AnnotationReference clone() {
        return (AnnotationReference) super.clone();
        //do not clone annotation that we're referring to. See wizardry in SpanTree for that.
    }
Clones this AnnotationReference.&nbsp;Note: No deep-copying, so the AnnotationReference returned
refers to the same Annotation as this AnnotationReference.

@return a copy of this object, referring to the same Annotation instance.
document/src/main/java/com/yahoo/document/annotation/AnnotationReference.java