code: public Observable<Page<CertificateInner>> listByAutomationAccountNextAsync(final String nextPageLink) {
          return listByAutomationAccountNextWithServiceResponseAsync(nextPageLink)
              .map(new Func1<ServiceResponse<Page<CertificateInner>>, Page<CertificateInner>>() {
                  @Override
                  public Page<CertificateInner> call(ServiceResponse<Page<CertificateInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Retrieve a list of certificates.
  
  @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;CertificateInner&gt; object