init function
Implementation
void init(InitRequest initReq) {
// Create ArucoDetector
_detector = _ArucoDetector();
// Save the port on which we will send messages to the main thread
_toMainThread = initReq.toMainThread;
// Create a port on which the main thread can send us messages and listen to it
ReceivePort fromMainThread = ReceivePort();
fromMainThread.listen(_handleMessage);
// Send the main thread the port on which it can send us messages
_toMainThread.send(fromMainThread.sendPort);
}