code: public Searcher registerResultListener(@NonNull AlgoliaResultsListener resultListener) {
          if (!resultListeners.contains(resultListener)) {
              resultListeners.add(resultListener);
          }
          return this;
      }
docs: Links the given listener to the Searcher, which will forward new search results to it.
  
  @param resultListener an object implementing {@link AlgoliaResultsListener}.