private List<Ports.Builder> getPorts(Service modelService) {
        List<Ports.Builder> ret = new ArrayList<>();
        PortsMeta portsMeta = modelService.getPortsMeta();
        for (int i = 0; i < portsMeta.getNumPorts(); i++) {
            ret.add(new Ports.Builder()
                    .number(modelService.getRelativePort(i))
                    .tags(getPortTags(portsMeta, i))
            );
        }
        return ret;
    }
Prepares the model for start. The {@link VespaModel} calls
this methods after it has loaded this and all plugins have been loaded and
their initialize() methods have been called.

@param plugins All initialized plugins of the vespa model.
config-model/src/main/java/com/yahoo/config/model/ApplicationConfigProducerRoot.java