code: public Observable<ServiceResponseWithHeaders<Page<Certificate>, CertificateListHeaders>> listNextSinglePageAsync(final String nextPageLink) {
          if (nextPageLink == null) {
              throw new IllegalArgumentException("Parameter nextPageLink is required and cannot be null.");
          }
          final CertificateListNextOptions certificateListNextOptions = null;
          UUID clientRequestId = null;
          Boolean returnClientRequestId = null;
          DateTime ocpDate = null;
          DateTimeRfc1123 ocpDateConverted = null;
          if (ocpDate != null) {
              ocpDateConverted = new DateTimeRfc1123(ocpDate);
          }
          String nextUrl = String.format("%s", nextPageLink);
          return service.listNext(nextUrl, this.client.acceptLanguage(), clientRequestId, returnClientRequestId, ocpDateConverted, this.client.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponseWithHeaders<Page<Certificate>, CertificateListHeaders>>>() {
                  @Override
                  public Observable<ServiceResponseWithHeaders<Page<Certificate>, CertificateListHeaders>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponseWithHeaders<PageImpl<Certificate>, CertificateListHeaders> result = listNextDelegate(response);
                          return Observable.just(new ServiceResponseWithHeaders<Page<Certificate>, CertificateListHeaders>(result.body(), result.headers(), result.response()));
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }
docs: Lists all of the certificates that have been added to the specified account.
  
  @param nextPageLink The NextLink from the previous successful call to List operation.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the PagedList&lt;Certificate&gt; object wrapped in {@link ServiceResponseWithHeaders} if successful.