code: public Observable<TrendingTopics> trendingAsync(TrendingOptionalParameter trendingOptionalParameter) {
          return trendingWithServiceResponseAsync(trendingOptionalParameter).map(new Func1<ServiceResponse<TrendingTopics>, TrendingTopics>() {
              @Override
              public TrendingTopics call(ServiceResponse<TrendingTopics> response) {
                  return response.body();
              }
          });
      }
docs: The News Trending Topics API lets lets you search on Bing and get back a list of trending news topics that are currently trending on Bing. This section provides technical details about the query parameters and headers that you use to request news and the JSON response objects that contain them.  For examples that show how to make requests, see [Searching the web for news](https://docs.microsoft.com/en-us/azure/cognitive-services/bing-news-search/search-the-web).
  
  @param trendingOptionalParameter the object representing the optional parameters to be set before calling this API
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the TrendingTopics object