why i can't use firebaseuser in vscode
Future<String> signIn(String email, String password) async {
FirebaseUser user = await
FirebaseAuth.instance.signInWithEmailAndPassword(
email: email, password: password);
return user.uid;
}
Future<String> createUser(String email, String password) async {
FirebaseUser user = await
FirebaseAuth.instance.createUserWithEmailAndPassword(
email: email, password: password);
return user.uid;
}