Source
factory Notification(String title, {String dir: null, String body: null,
String lang: null, String tag: null, String icon: null}) {
var parsedOptions = {};
if (dir != null) parsedOptions['dir'] = dir;
if (body != null) parsedOptions['body'] = body;
if (lang != null) parsedOptions['lang'] = lang;
if (tag != null) parsedOptions['tag'] = tag;
if (icon != null) parsedOptions['icon'] = icon;
return Notification._factoryNotification(title, parsedOptions);
}