docs: public Observable<Page<AppServiceCertificateResourceInner>> listCertificatesNextAsync(final String nextPageLink) {
          return listCertificatesNextWithServiceResponseAsync(nextPageLink)
              .map(new Func1<ServiceResponse<Page<AppServiceCertificateResourceInner>>, Page<AppServiceCertificateResourceInner>>() {
                  @Override
                  public Page<AppServiceCertificateResourceInner> call(ServiceResponse<Page<AppServiceCertificateResourceInner>> response) {
                      return response.body();
                  }
              });
      }