try {
  const result = await retrieveLatestBackupInfo('username123');
  if (result === null) {
    console.log('backup not found');
  } else {
    console.log('backup found', result);
  }
} catch (e) {
  const msg = getMessageForException(e);
  if (msg === 'user_not_found') {
    console.log('user not found');
  } else {
    console.log('error: ' + msg);
  }
}
`