code: public Observable<ServiceResponse<Page<ApplicationGatewayInner>>> listAllSinglePageAsync() {
          if (this.client.subscriptionId() == null) {
              throw new IllegalArgumentException("Parameter this.client.subscriptionId() is required and cannot be null.");
          }
          final String apiVersion = "2017-10-01";
          return service.listAll(this.client.subscriptionId(), apiVersion, this.client.acceptLanguage(), this.client.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponse<Page<ApplicationGatewayInner>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<ApplicationGatewayInner>>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponse<PageImpl<ApplicationGatewayInner>> result = listAllDelegate(response);
                          return Observable.just(new ServiceResponse<Page<ApplicationGatewayInner>>(result.body(), result.response()));
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }
docs: Gets all the application gateways in a subscription.
  
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the PagedList&lt;ApplicationGatewayInner&gt; object wrapped in {@link ServiceResponse} if successful.