toJson method
Implementation
Map<String, dynamic> toJson() => {
'v': version, // 'v' instead of 'version' per spec
if (clid != null) 'clid': clid,
if (url != null) 'url': url,
if (cldf != null) 'cldf': cldf,
if (route != null) 'route': route,
if (loc != null) 'loc': loc,
if (meta != null) 'meta': meta,
if (verification != null) 'verification': verification,
};