code: public Observable<Void> purgeDeletedSecretAsync(String vaultBaseUrl, String secretName) {
          return purgeDeletedSecretWithServiceResponseAsync(vaultBaseUrl, secretName).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }
docs: Permanently deletes the specified secret.
  The purge deleted secret operation removes the secret permanently, without the possibility of recovery. This operation can only be enabled on a soft-delete enabled vault. This operation requires the secrets/purge 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 {@link ServiceResponse} object if successful.