def METHOD_NAME(disont_id):
    """for a disease ontology ID (including prefix "DOID:", with zero padding), return child DOIDs
    :param disont_id: string, like ``'DOID:14069'``
    :returns: ``set`` with keys as DOIDs
    """
    res = QueryDisont.send_query_get('metadata', disont_id)
    ret_set = set()
    if res is not None:
        res_json = res.json()