* Rank fusion searchers are responsible for executing search queries and
 * can be combined to implement advanced ranking strategies.
 */
public abstract class RankFusionSearcher {
    /** The name of this searcher, lazily initialized. */
    protected String name;

    /**
     * Default constructor for creating a new rank fusion searcher instance.

     */
    static class TestSearcher extends RankFusionSearcher {
        @Override
        protected SearchResult search(String query, SearchRequestParams params, OptionalThing<FessUserBean> userBean) {
            return SearchResult.create().build();
        }
    }

    /**
     * Custom searcher implementation.
     */
    static class CustomSearcher extends RankFusionSearcher {
        @Override