code: public Observable<BackupSecretResult> backupSecretAsync(String vaultBaseUrl, String secretName) {
          return backupSecretWithServiceResponseAsync(vaultBaseUrl, secretName).map(new Func1<ServiceResponse<BackupSecretResult>, BackupSecretResult>() {
              @Override
              public BackupSecretResult call(ServiceResponse<BackupSecretResult> response) {
                  return response.body();
              }
          });
      }
docs: Backs up the specified secret.
  Requests that a backup of the specified secret be downloaded to the client. All versions of the secret will be downloaded. This operation requires the secrets/backup permission.
  
  @param vaultBaseUrl The vault name, for example https://myvault.vault.azure.net.
  @param secretName The name of the secret.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the BackupSecretResult object