whenOrNull<TResult extends Object?>  method 
      
  
TResult?
whenOrNull<TResult extends Object?>( 
    
- TResult? $default(- String method,
- TokensObject input,
- TokensObject output
 
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( String method,  TokensObject input,  TokensObject output)?  $default,) {final _that = this;
switch (_that) {
case _DecodedTransaction() when $default != null:
return $default(_that.method,_that.input,_that.output);case _:
  return null;
}
}