public void Accept(IComboVisitor visitor)
 {
     foreach (var asset in Assets)
     {
         if (asset is Sandwiche)
         {
             foreach (var asseting in ((Sandwiche)asset).Assets)
             {
                    asseting.Accept(visitor);
             }
         }
         asset.Accept(visitor);
     }
 }
 public void Accept(IComboVisitor visitor)
 {
     visitor.Visit(this);
 }