code: def _token_request(self, grant_type, **kwargs):
          
          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)
docs: Do the actual call to the token end-point.
  
          :param grant_type:
          :param kwargs: See invoking methods.
          :return: