start method
Implementation
Future<bool?> start({final Function? onRecognitionError}) {
_errorStreamSubscription ??= EventChannel(
'error_event_channel',
const StandardMethodCodec(),
_channel.binaryMessenger,
).receiveBroadcastStream().listen(null, onError: onRecognitionError);
return _channel.invokeMethod<bool>('speechService.start');
}