maybeWhen<TResult extends Object?>  method 
- @optionalTypeArgs
A variant of when that fallback to an orElse callback.
It is equivalent to doing:
switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case _:
    return orElse();
}
Implementation
@optionalTypeArgs TResult maybeWhen<TResult extends Object?>(TResult Function( String return_url,  String? confirmation_token)?  $default,{required TResult orElse(),}) {final _that = this;
switch (_that) {
case _ConfirmSetupParams() when $default != null:
return $default(_that.return_url,_that.confirmation_token);case _:
  return orElse();
}
}