code: def logged_in():
      
      error = request.args.get('error')
      state = request.args.get('state')
      if error:
          return render_template('login_error.html', error=error)
      else:
          code = request.args.get('code')
          client = Client()
          access_token = client.exchange_code_for_token(client_id=app.config['STRAVA_CLIENT_ID'],
                                                        client_secret=app.config['STRAVA_CLIENT_SECRET'],
                                                        code=code)
          # Probably here you'd want to store this somewhere -- e.g. in a database.
          strava_athlete = client.get_athlete()
  
          return render_template('login_results.html', athlete=strava_athlete, access_token=access_token)
docs: Method called by Strava (redirect) that includes parameters.
      - state
      - code
      - error