public static IUndoState RemoveItems(this UserBlackMarketData userData, Dictionary <BlackMarketItemId, int> bmiCountById) => default;
 public static IUndoState RemoveItem(this UserBlackMarketData userData, BlackMarketItemId itemId, int count = 1) => default;
 public static IUndoState AddItem(this UserBlackMarketData userData, BlackMarketItemId itemId, int count    = 1, DateTime?expiryDate = default) => default;
 public static void AssertItemExist(this UserBlackMarketData userData, BlackMarketItemId itemId)
 {
 }
 public static List <BmiBox> AssertItemsExist(this UserBlackMarketData userData, Dictionary <BlackMarketItemId, int> bmiCountById) => default;
 public static BmiBox AssertItemExists(this UserBlackMarketData userData, BlackMarketItemId itemId, int count = 1) => default;