def METHOD_NAME(case_factory, event):
    old_case_id = _get_old_case_id(event)
    ext_case_ids = CommCareCaseIndex.objects.get_extension_case_ids(
        event.domain,
        [old_case_id],
        include_closed=False,
    )
    case_factory.create_or_update_cases([
        CaseStructure(case_id=case_id, attrs={'close': True})
        for case_id in ext_case_ids
    ])