public static Identifiable createFromId(int id) {
        return registry.createFromId(id);
    }
Creates an instance of the class registered with the given identifier. If the indentifier is unknown, this method
returns null.

@param id The identifier of the class to instantiate.
@return The instantiated object.
vespajlib/src/main/java/com/yahoo/vespa/objects/Identifiable.java