bidi method
Implementation
Future<DynamicStream> bidi(String service, String method,
List<GenericMessage> reqs,
{Map<String, String>? metadata, Duration? timeout}) async {
final m = _method(service, method);
final bound = reqs.map((r) => _BoundMessage(m.input!, r, _model)).toList();
final stream = await _channel.bidi(m.path, bound, metadata: metadata, timeout: timeout);
return DynamicStream(stream, m.output!, _model);
}