public SpanTree annotate(SpanNode node, AnnotationType type,FieldValue value) {
        return annotate(node, new Annotation(type, value));
    }
Adds an Annotation.
Convenience shorthand for <code>annotate(node,new Annotation(type,value)</code>

@param node the node to annotate
@param type the type of the Annotation to add
@param value the value of the Annotation to add
@return this, for chaining
@see com.yahoo.document.annotation.Annotation
document/src/main/java/com/yahoo/document/annotation/SpanTree.java