code: public ServiceFuture<List<KeyItem>> listKeysAsync(final String vaultBaseUrl,
              final ListOperationCallback<KeyItem> serviceCallback) {
          return getKeysAsync(vaultBaseUrl, serviceCallback);
      }
docs: List keys in the specified vault.
  
  @param vaultBaseUrl
  The vault name, e.g. https://myvault.vault.azure.net
  @param serviceCallback
  the async ServiceCallback to handle successful and failed
  responses.
  @return the {@link ServiceFuture} object