@Override
    protected SearchChainsBuilder readChains(DeployState deployState, TreeConfigProducer<AnyConfigProducer> ancestor, List<Element> searchChainsElements,
                                             Map<String, ComponentType<?>> outerComponentTypeByComponentName) {
        return new SearchChainsBuilder(deployState, ancestor, searchChainsElements, outerComponentTypeByComponentName);
    }
Builds the search chains model from xml.

@author Tony Vaagenes
config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/chains/search/DomSearchChainsBuilder.java