private String errorMsgClassName() {
        if (getClass().equals(SimpleConfigProducer.class)) return getParent().getClass().getSimpleName();
        return getClass().getSimpleName();
    }
Helper to provide an error message on collisions of sub ids (ignore SimpleConfigProducer, use the parent in that case)
config-model/src/main/java/com/yahoo/config/model/producer/TreeConfigProducer.java