The embedder can specify data that the isolate can request synchronously on launch. This accessor fetches that data.
This data is persistent for the duration of the Flutter application and is available even after isolate restarts. Because of this lifecycle, the size of this data must be kept to a minimum.
For asynchronous communication between the embedder and isolate, a platform channel may be used.
@override ByteData? getPersistentIsolateData() => _platformDispatcher.getPersistentIsolateData();