serialize method
Implementation
@override
String serialize() {
var out = StringBuffer()
..writecrlf('BEGIN:VCALENDAR')
..writecrlf('VERSION:2.0')
..writecrlf('PRODID://$company//$product//${lang}');
if (refreshInterval != null) {
out.writecrlf(
'REFRESH-INTERVAL;VALUE=DURATION:${utils.formatDuration(refreshInterval!)}');
}
for (ICalendarElement element in _elements) {
out.write(element.serialize());
}
out.writecrlf('END:VCALENDAR');
return out.toString();
}