firebase authentication guide GOOGLE_GUID?

Trying to do the Google authentication for Firebase. The guide code says

clientId: 'Your-Web-Client-ID.apps.googleusercontent.com', 
redirectUri: makeRedirectUri({
// For usage in bare and standalone 
native: 'com.googleusercontent.apps.GOOGLE_GUID:/oauthredirect',

I know how to get the web client ID but where do I find the GOOGLE_GUID on Firebase or Google?