addObserver method
Implementation
void addObserver(String path,
Future<Map<String, dynamic>?> Function(Map<String, dynamic>?) callback) {
throw UnimplementedError('platformVersion() has not been implemented.');
}
void addObserver(String path,
Future<Map<String, dynamic>?> Function(Map<String, dynamic>?) callback) {
throw UnimplementedError('platformVersion() has not been implemented.');
}