Dart APIlicense_listLicenseListSliveronSelectPackage onSelectPackage property Null safety dynamic Function(String packageName) onSelectPackage final Implementation final Function(String packageName) onSelectPackage; unself_license_list license_list LicenseListSliver onSelectPackage property LicenseListSliver class Constructors LicenseListSliver Properties hashCode key onSelectPackage runtimeType Methods build createElement debugDescribeChildren debugFillProperties noSuchMethod toDiagnosticsNode toString toStringDeep toStringShallow toStringShort Operators operator == Static methods item