How to use the home-assistant-js-websocket.genExpires function in home-assistant-js-websocket

method: 'POST',
    credentials: 'same-origin',
    body: formData
  });

  if (!resp.ok) {
    throw resp.status === 400 /* auth invalid */ ||
    resp.status === 403 /* user not active */
      ? ERR_INVALID_AUTH
      : new Error('Unable to fetch tokens');
  }

  const tokens: AuthData = await resp.json();
  tokens.hassUrl = hassUrl;
  tokens.clientId = clientId;
  tokens.expires = genExpires(tokens.expires_in);
  return tokens;
}