code: public ServiceFuture<Void> purgeDeletedKeyAsync(String vaultBaseUrl, String keyName, final ServiceCallback<Void> serviceCallback) {
          return ServiceFuture.fromResponse(purgeDeletedKeyWithServiceResponseAsync(vaultBaseUrl, keyName), serviceCallback);
      }
docs: Permanently deletes the specified key.
  The Purge Deleted Key operation is applicable for soft-delete enabled vaults. 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/purge permission.
  
  @param vaultBaseUrl The vault name, for example https://myvault.vault.azure.net.
  @param keyName The name of the key
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object