disconnect method Null safety
Disconnects all channels that have been transformed.
Returns a future that completes when all inner sinks' StreamSink.close futures have completed. Note that a StreamController's sink won't close until the corresponding stream has a listener.
Implementation
Future<void> disconnect() => _disconnectMemo.runOnce(() {
var futures = _sinks.map((sink) => sink._disconnect()).toList();
_sinks.clear();
return Future.wait(futures, eagerError: true);
});