docs: public Observable<ServiceResponse<Page<BackupEngineBaseResourceInner>>> getSinglePageAsync(final String vaultName, final String resourceGroupName, final String filter, final String skipToken) {
          if (vaultName == null) {
              throw new IllegalArgumentException("Parameter vaultName is required and cannot be null.");
          }
          if (resourceGroupName == null) {
              throw new IllegalArgumentException("Parameter resourceGroupName is required and cannot be null.");
          }
          if (this.client.subscriptionId() == null) {
              throw new IllegalArgumentException("Parameter this.client.subscriptionId() is required and cannot be null.");
          }
          if (this.client.apiVersion() == null) {
              throw new IllegalArgumentException("Parameter this.client.apiVersion() is required and cannot be null.");
          }
          return service.get(vaultName, resourceGroupName, this.client.subscriptionId(), this.client.apiVersion(), filter, skipToken, this.client.acceptLanguage(), this.client.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponse<Page<BackupEngineBaseResourceInner>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<BackupEngineBaseResourceInner>>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponse<PageImpl1<BackupEngineBaseResourceInner>> result = getDelegate(response);
                          return Observable.just(new ServiceResponse<Page<BackupEngineBaseResourceInner>>(result.body(), result.response()));
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }