Download an object.

        :param str instance: A Yamcs instance name.
        :param str bucket_name: The name of the bucket.
        :param str object_name: The object to fetch.

def download_object(self, instance, bucket_name, object_name):
        """
        Download an object.

        :param str instance: A Yamcs instance name.
        :param str bucket_name: The name of the bucket.
        :param str object_name: The object to fetch.
        """
        url = '/buckets/{}/{}/{}'.format(instance, bucket_name, object_name)
        response = self._client.get_proto(path=url)
        return response.content