whenOrNull<TResult extends Object?>  method 
- @optionalTypeArgs
A variant of when that fallback to returning null
It is equivalent to doing:
switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case _:
    return null;
}
Implementation
@optionalTypeArgs TResult? whenOrNull<TResult extends Object?>({TResult? Function( Map<String, dynamic> data)?  unknown,}) {final _that = this;
switch (_that) {
case UVerificationViewIssuerProfileUnknown() when unknown != null:
return unknown(_that.data);case _:
  return null;
}
}