@Override
    public String toString() {
        ObjectDumper ret = new ObjectDumper();
        ret.visit("", this);
        return ret.toString();
    }
Declares that all subclasses of Identifiable supports clone() by _not_ throwing CloneNotSupported exceptions.

@return A cloned instance of this.
@throws AssertionError Thrown if a subclass does not implement clone().
vespajlib/src/main/java/com/yahoo/vespa/objects/Identifiable.java