Fetch the data for the model from Redis and assign the values.

        :param method callback: The callback method to invoke when done

def fetch(self):
        """Fetch the data for the model from Redis and assign the values.

        :param method callback: The callback method to invoke when done

        """
        LOGGER.debug('Fetching session data: %s', self.id)
        result = yield gen.Task(RedisSession._redis_client.get, self._key)
        if result:
            self.loads(result)
            raise gen.Return(True)
        else:
            raise gen.Return(False)