public ICalzone AddTopping(ITopping topping) => _type.Create(_toppings.Add(topping));
public IPizza AddTopping(ITopping topping) => _type.Create(_toppings.Add(topping));
public ICalzone AddTopping(ITopping topping) => _type.Create(_toppings.Add(topping));
public IPizza AddTopping(ITopping topping) => _type.Create(_toppings.Add(topping));