How to use the @polkadot/ui-keyring.backupAccount function in @polkadot/ui-keyring

const _doBackup = (): void => {
    try {
      const addressKeyring = address && keyring.getPair(address);
      const json = addressKeyring && keyring.backupAccount(addressKeyring, password);
      const blob = new Blob([JSON.stringify(json)], { type: 'application/json; charset=utf-8' });

      FileSaver.saveAs(blob, `${address}.json`);
    } catch (error) {
      setBackupFailed(true);
      console.error(error);
      return;
    }

    onClose();
  };

private accountsExport ({ address, password }: RequestAccountExport): ResponseAccountExport {
    return { exportedJson: JSON.stringify(keyring.backupAccount(keyring.getPair(address), password)) };
  }