getOuterPath method Null safety
override
    Creates a Path that describes the outline of the shape.
The host is the bounding rectangle of the shape.
The guest is the bounding rectangle of the shape for which a notch will
be made. It is null when there is no guest.
Implementation
@override
Path getOuterPath(Rect hostRect, Rect? guestRect) { // ignore: avoid_renaming_method_parameters
  // The parameters of this method are renamed over the baseclass because they
  // would clash with properties of this object, and the use of all four of
  // them in the code below is really confusing if they have the same names.
  final Path hostPath = host.getOuterPath(hostRect);
  if (guest != null && guestRect != null) {
    final Path guestPath = guest!.getOuterPath(guestRect);
    return Path.combine(PathOperation.difference, hostPath, guestPath);
  }
  return hostPath;
}