docs: def get_authenticated_user(self, callback):
          """Fetches the authenticated user data upon redirect.
  
          This method should be called by the handler that receives the
          redirect from the authenticate_redirect() or authorize_redirect()
          methods.
          """
          # Verify the OpenID response via direct request to the OP
          args = dict((k, v) for k, v in request.args.items())
          args["openid.mode"] = u"check_authentication"
  
          r = requests.post(self._OPENID_ENDPOINT, data=args)
          return self._on_authentication_verified(callback, r)