<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _token_request(self, grant_type, **kwargs):
 """ Do the actual call to the token end-point. :param grant_type: :param kwargs: See invoking methods. :return: """

        payload = {
            'grant_type': grant_type,
            'client_id': self._client_id,
            'client_secret': self._client_secret
        }

        payload.update(**kwargs)

        return self._realm.client.post(self.get_url('token_endpoint'),
                                       data=payload)