How to use the elasticsearch2.helpers.reindex function in elasticsearch2

def set_up_index(idx):
    alias = es_client().indices.get_aliases(index=idx)

    if not alias or not alias.keys() or idx in alias.keys():
        # Deal with empty indices or the first migration
        index = '{}_v1'.format(idx)
        search.create_index(index=index)
        logger.info('Reindexing {0} to {1}_v1'.format(idx, idx))
        helpers.reindex(es_client(), idx, index)
        logger.info('Deleting {} index'.format(idx))
        es_client().indices.delete(index=idx)
        es_client().indices.put_alias(index=index, name=idx)
    else:
        # Increment version
        version = int(list(alias.keys())[0].split('_v')[1]) + 1
        logger.info('Incrementing index version to {}'.format(version))
        index = '{0}_v{1}'.format(idx, version)
        search.create_index(index=index)
        logger.info('{} index created'.format(index))
    return index