@Override
    public MODEL build(ConfigModelInstanceFactory<MODEL> factory, Element spec, ConfigModelContext context) {
        VespaDomBuilder.DomSimpleConfigProducerBuilder builder = new VespaDomBuilder.DomSimpleConfigProducerBuilder(context.getProducerId());
        TreeConfigProducer<AnyConfigProducer> producer = builder.build(context.getDeployState(), context.getParentProducer(), spec);
        return super.build(factory, spec, context.withParent(producer));
    }
A model builder that can be used to deal with toplevel config overrides and create another
producer in between. This should not be used by new model plugins.

@author Ulf Lilleengen
config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/LegacyConfigModelBuilder.java