code: public Observable<ServiceResponse<Page<DeletedCertificateItem>>> getDeletedCertificatesNextWithServiceResponseAsync(final String nextPageLink) {
          return getDeletedCertificatesNextSinglePageAsync(nextPageLink)
              .concatMap(new Func1<ServiceResponse<Page<DeletedCertificateItem>>, Observable<ServiceResponse<Page<DeletedCertificateItem>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<DeletedCertificateItem>>> call(ServiceResponse<Page<DeletedCertificateItem>> page) {
                      String nextPageLink = page.body().nextPageLink();
                      if (nextPageLink == null) {
                          return Observable.just(page);
                      }
                      return Observable.just(page).concatWith(getDeletedCertificatesNextWithServiceResponseAsync(nextPageLink));
                  }
              });
      }
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 observable to the PagedList&lt;DeletedCertificateItem&gt; object