Python Flask Log in with OAuth Google [closed]

I am trying to make an application in which users register using an account in Google and Github services. I can not even have them registered by google, and my best attempt was made from:   link

The problem is that my html is more complex which is:

html code I do not understand how to implement the login function so that I can interact with google tokens, so for example on the official Flask website I have the following example:

@app.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        login_user(user)
        flask.flash('Logged in successfully.')
        next = flask.request.args.get('next')
        if not next_is_valid(next):
            return flask.abort(400)
        return flask.redirect(next or flask.url_for('index'))
    return flask.render_template('login.html', form=form)

But, it does not make clear where you can process the tokens of ancillary services, such as google for example.