def _offset(self, partition, timestamp):
        while True:
            future = self._send_offset_request(partition, timestamp)
            self._client.poll(future=future)

            if future.succeeded():
                return future.value

            if not future.retriable():
                raise future.exception # pylint: disable-msg=raising-bad-type

            if future.exception.invalid_metadata:
                refresh_future = self._client.cluster.request_update()
                self._client.poll(future=refresh_future, sleep=True)
Calculate Kendall's tau between ``y_true`` and ``y_pred``.
dataset/ETHPy150Open dpkp/kafka-python/kafka/consumer/fetcher.py/Fetcher._offset--crossover with--dataset/ETHPy150Open EducationalTestingService/skll/skll/metrics.py/kendall_tau