toJson method 
    
    
    
  Implementation
  @override
Map<String, dynamic> toJson([dynamic extra]) {
  return {
    "@type": CONSTRUCTOR,
    "id": id,
    "is_current": isCurrent,
    "is_password_pending": isPasswordPending,
    "can_accept_secret_chats": canAcceptSecretChats,
    "can_accept_calls": canAcceptCalls,
    "type": type.toJson(),
    "api_id": apiId,
    "application_name": applicationName,
    "application_version": applicationVersion,
    "is_official_application": isOfficialApplication,
    "device_model": deviceModel,
    "platform": platform,
    "system_version": systemVersion,
    "log_in_date": logInDate,
    "last_active_date": lastActiveDate,
    "ip": ip,
    "country": country,
    "region": region,
  };
}