code: public Observable<ServiceResponse<Page<DeletedCertificateItem>>> getDeletedCertificatesNextSinglePageAsync(final String nextPageLink) {
          if (nextPageLink == null) {
              throw new IllegalArgumentException("Parameter nextPageLink is required and cannot be null.");
          }
          String nextUrl = String.format("%s", nextPageLink);
          return service.getDeletedCertificatesNext(nextUrl, this.acceptLanguage(), this.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponse<Page<DeletedCertificateItem>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<DeletedCertificateItem>>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponse<PageImpl<DeletedCertificateItem>> result = getDeletedCertificatesNextDelegate(response);
                          return Observable.just(new ServiceResponse<Page<DeletedCertificateItem>>(result.body(), result.response()));
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }
docs: Lists the deleted certificates in the specified vault currently available for recovery.
  The GetDeletedCertificates operation retrieves the certificates in the current vault which are in a deleted state and ready for recovery or purging. This operation includes deletion-specific information. This operation requires the certificates/get/list permission. This operation can only be enabled on soft-delete enabled vaults.
  
  @param nextPageLink The NextLink from the previous successful call to List operation.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the PagedList&lt;DeletedCertificateItem&gt; object wrapped in {@link ServiceResponse} if successful.