in lib/src/arg_parser.dart [248:272]
void addMultiOption(String name,
{String? abbr,
String? help,
String? valueHelp,
Iterable<String>? allowed,
Map<String, String>? allowedHelp,
Iterable<String>? defaultsTo,
void Function(List<String>)? callback,
bool splitCommas = true,
bool hide = false,
List<String> aliases = const []}) {
_addOption(
name,
abbr,
help,
valueHelp,
allowed,
allowedHelp,
defaultsTo?.toList() ?? <String>[],
callback == null ? null : (value) => callback(value as List<String>),
OptionType.multiple,
splitCommas: splitCommas,
hide: hide,
aliases: aliases);
}