code: public Observable<ServiceResponse<FoundFaces>> findFacesWithServiceResponseAsync(Boolean cacheImage) {
          if (this.client.baseUrl() == null) {
              throw new IllegalArgumentException("Parameter this.client.baseUrl() is required and cannot be null.");
          }
          String parameterizedHost = Joiner.on(", ").join("{baseUrl}", this.client.baseUrl());
          return service.findFaces(cacheImage, this.client.acceptLanguage(), parameterizedHost, this.client.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponse<FoundFaces>>>() {
                  @Override
                  public Observable<ServiceResponse<FoundFaces>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponse<FoundFaces> clientResponse = findFacesDelegate(response);
                          return Observable.just(clientResponse);
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }
docs: Returns the list of faces found.
  
  @param cacheImage Whether to retain the submitted image for future use; defaults to false if omitted.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the FoundFaces object