code: def _get_flow_for_token(csrf_token, request):
      
      flow_pickle = request.session.get(_FLOW_KEY.format(csrf_token), None)
      return None if flow_pickle is None else jsonpickle.decode(flow_pickle)
docs: Looks up the flow in session to recover information about requested
      scopes.
  
      Args:
          csrf_token: The token passed in the callback request that should
              match the one previously generated and stored in the request on the
              initial authorization view.
  
      Returns:
          The OAuth2 Flow object associated with this flow based on the
          CSRF token.