@Override
    void aggregateDescendantServices() {
        for (CHILD child : childrenBySubId.values()) {
            child.aggregateDescendantServices();
            descendantServices.addAll(child.getDescendantServices());
        }
    }
Returns a list of all the children of this who are instances of Service
config-model/src/main/java/com/yahoo/config/model/producer/TreeConfigProducer.java