Idiomatic Ruby would not use inheritance in this case. 'Node' is a duck type and doesn't need to be explicitly defined. In 2004 this would have been written for

Idiomatic Ruby would not use inheritance in this case. 'Node' is a duck type and doesn't need to be explicitly defined. In 2004 this would have been written for an audience more conversant in C++ and Java, where you'd need to use an abstract base class and an interface respectively.