public SpanTree annotate(SpanNode node, AnnotationType type) {
        Annotation a = new Annotation(type);
        return annotate(node, a);
    }
Creates an Annotation based on the given AnnotationType, and adds it to the internal list of
annotations for this SpanTree (convenience method).&nbsp;Use this when
adding an Annotation (that does not have a FieldValue) that shall annotate a SpanNode.
Upon return, Annotation.getSpanNode()
returns the given node.

@param node the node to annotate
@param type the AnnotationType to create an Annotation from
@return this, for chaining
@see com.yahoo.document.annotation.Annotation
@see com.yahoo.document.annotation.AnnotationType
document/src/main/java/com/yahoo/document/annotation/SpanTree.java