transfer method Null safety

Future<void> transfer(
  1. String uri,
  2. {String? replace}
)

transfer on-going call to another sip uri uri : SIP URI to send the transferee too replace: call-ID of the call this attended transfer is supposed to replace; default is none, which means blind/unattended transfer

Implementation

Future<void> transfer(
  String uri, {
  String? replace,
}) async {
  var payload = {"request": "transfer", "uri": uri, "replace": replace}
    ..removeWhere((key, value) => value == null);
  JanusEvent response = JanusEvent.fromJson(await this.send(data: payload));
  JanusError.throwErrorFromEvent(response);
}