How to use the keystonemiddleware.auth_token._user_plugin.UserAuthPlugin function in keystonemiddleware

request.user_token_valid = True
                request.token_info = data

        if request.service_token:
            self.log.debug('Authenticating service token')
            try:
                _, serv_auth_ref = self._do_fetch_token(request.service_token)
                self._validate_token(serv_auth_ref)
                self._confirm_token_bind(serv_auth_ref, request)
            except ksm_exceptions.InvalidToken:
                self.log.info(_LI('Invalid service token'))
                request.service_token_valid = False
            else:
                request.service_token_valid = True

        request.token_auth = _user_plugin.UserAuthPlugin(user_auth_ref,
                                                         serv_auth_ref)

try:
                data, user_auth_ref = self._do_fetch_token(
                    request.user_token,
                    allow_expired=allow_expired)
                self._validate_token(user_auth_ref,
                                     allow_expired=allow_expired)
                if not request.service_token:
                    self._confirm_token_bind(user_auth_ref, request)
            except ksm_exceptions.InvalidToken:
                self.log.info('Invalid user token')
                request.user_token_valid = False
            else:
                request.user_token_valid = True
                request.token_info = data

        request.token_auth = _user_plugin.UserAuthPlugin(user_auth_ref,
                                                         serv_auth_ref)

def get_headers(self, session, **kwargs):
        headers = super(UserAuthPlugin, self).get_headers(session, **kwargs)

        if headers is not None and self._session:
            token = self._session.get_token(auth=self._auth)

            if token:
                headers['X-Service-Token'] = token

        return headers