def METHOD_NAME(value):
    if value == '*':
        return Level.objects.filter(on_top_of__isnull=True)
    values = set(v for v in value.split(',') if v)
    levels = Level.objects.filter(on_top_of__isnull=True, short_label__in=values)
    not_found = values - set(level.short_label for level in levels)
    if not_found:
        raise argparse.ArgumentTypeError(
            ngettext_lazy('Unknown level: %s', 'Unknown levels: %s', len(not_found)) % ', '.join(not_found)
        )
    return levels