def _save_multi(data, file_name, sep=";"):
    """convenience function for storing data column-wise in a csv-file."""
    logger.debug("saving multi")
    with open(file_name, "w", newline='') as f:
        logger.debug(f"{file_name} opened")
        writer = csv.writer(f, delimiter=sep)
        try:
            writer.writerows(itertools.zip_longest(*data))
        except Exception as e:
            logger.info(f"Exception encountered in batch._save_multi: {e}")
            raise ExportFailed
        logger.debug("wrote rows using itertools in _save_multi")
convenience function for storing data column-wise in a csv-file.