code: 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();
                  }
              });
      }
docs: List all certificates associated with a certificate order.
  List all certificates associated with a certificate order.
  
  @param nextPageLink The NextLink from the previous successful call to List operation.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;AppServiceCertificateResourceInner&gt; object