toJson method
Implementation
Map<String, dynamic> toJson() => {
if (userAgent != null) 'userAgent': userAgent,
if (platform != null) 'platform': platform,
if (language != null) 'language': language,
if (tz != null) 'tz': tz,
if (screen != null) 'screen': {'w': screen!.w, 'h': screen!.h},
};