code: public Observable<ServiceResponse<Page<DeletedKeyItem>>> getDeletedKeysWithServiceResponseAsync(final String vaultBaseUrl) {
          return getDeletedKeysSinglePageAsync(vaultBaseUrl)
              .concatMap(new Func1<ServiceResponse<Page<DeletedKeyItem>>, Observable<ServiceResponse<Page<DeletedKeyItem>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<DeletedKeyItem>>> call(ServiceResponse<Page<DeletedKeyItem>> page) {
                      String nextPageLink = page.body().nextPageLink();
                      if (nextPageLink == null) {
                          return Observable.just(page);
                      }
                      return Observable.just(page).concatWith(getDeletedKeysNextWithServiceResponseAsync(nextPageLink));
                  }
              });
      }
docs: Lists the deleted keys in the specified vault.
  Retrieves a list of the keys in the Key Vault as JSON Web Key structures that contain the public part of a deleted key. This operation includes deletion-specific information. The Get Deleted Keys operation is applicable for vaults enabled for soft-delete. While the operation can be invoked on any vault, it will return an error if invoked on a non soft-delete enabled vault. This operation requires the keys/list permission.
  
  @param vaultBaseUrl The vault name, for example https://myvault.vault.azure.net.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;DeletedKeyItem&gt; object