when method
      
TransitionHandlerWhenWithDataBuilder<D> 
when(
    
    
- FutureOr<bool> condition(- TransitionContext msgCtx,
- D data
 
- void buildTrueHandler(), {
- String? label,
Implementation
TransitionHandlerWhenWithDataBuilder<D> when(
  FutureOr<bool> Function(TransitionContext msgCtx, D data) condition,
  void Function(TransitionHandlerBuilderWithData<D>) buildTrueHandler, {
  String? label,
}) {
  var trueBuilder = TransitionHandlerBuilderWithData<D>._(_forState);
  buildTrueHandler(trueBuilder);
  _conditions.add(_TransitionConditionWithContext(
    condition,
    trueBuilder._handler!,
    label,
  ));
  return this;
}