match<T>  method 
Implementation
T match<T>({
  required T Function(RoadEvent value) event,
  required T Function(AddEventError value) error,
}) {
  return switch (this._index) {
    0 => event(this._value as RoadEvent),
    1 => error(this._value as AddEventError),
    _ => throw NativeException("Unrecognized case index ${this._index}")
  };
}