title: Which among these is the proper implementation of the Memento design pattern?
body: <p>In GOF Book, it says the structure of the Memento design pattern is like this:
  <img src="https://ss0.bdstatic.com/70cFvHSh_Q1YnxGkpoWK1HF6hhy/it/u=2874087397,967157291&amp;fm=26&amp;gp=0.jpg" alt="GOF Memento Pattern"><br>
  But when I searched Wikipedia, it says the structure of  the Memento design pattern is like this:
  <img src="https://upload.wikimedia.org/wikipedia/commons/3/38/W3sDesign_Memento_Design_Pattern_UML.jpg" alt=""></p>
  
  <p>Which among the both is the correct implementation?</p>