Upgrade the index to the latest format.

        Any additional keyword arguments will be passed to
        ``Elasticsearch.indices.upgrade`` unchanged.

def upgrade(self, using=None, **kwargs):
        """
        Upgrade the index to the latest format.

        Any additional keyword arguments will be passed to
        ``Elasticsearch.indices.upgrade`` unchanged.
        """
        return self._get_connection(using).indices.upgrade(index=self._name, **kwargs)