Spam
        toString        Yam
        a               Yam a    Ham a    Spam b
        b               Spam b

Yam
        toString        Yam
        a               Yam a    Ham a    Lamb b
        b               Lamb b
        
Ham
        toString        Ham
        a               Ham a    Ham b
        b               Ham b
        

Lamb
        toString        Ham
        a               Ham a    Lamb b
        b               Lamb b