def METHOD_NAME(self, callback_url):
    session['oauth_state'] = token_urlsafe()
    session['oauth_callback'] = callback_url
    return redirect(
        furl(self.auth_url)
        .add(
            {
                'client_id': self.key,
                'redirect_uri': callback_url,
                'scope': 'r_liteprofile r_emailaddress',
                'state': session['oauth_state'],
            }
        )
        .url
    )