private void addChains(CHAINS chains, ChainsBuilder<COMPONENT, CHAIN> chainsBuilder) {
        for (CHAIN chain : chainsBuilder.getChains()) {
            chains.add(chain);
        }
    }
NOTE: This class _must_ be abstract, due to calling subclass method in ctor.
@author Tony Vaagenes
@author gjoranv
config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/chains/DomChainsBuilder.java