title: Ruby Class Diagram does not display in the Diagram menu of RubyMIne
body: <p>I have a Ruby on Rails project in RubyMine IDE so I want to generate the Class Diagram and when I click on 'Diagrams->Show Diagrams' teh IDE displays just: </p>
  
  <ul>
  <li>Rails Model Dependency Diagram  </li>
  <li>Gem Dependency Diagram</li>
  </ul>
  
  <p>I've checked the Ruby Class Diagram in the IDE Settings. Can someone help me to find out how to generate the Ruby Class Diagram with RubyMine please.!</p>
  
  <p><img src="https://i.stack.imgur.com/39RsZ.png" alt="enter image description here"></p>