title: How to make QCombobox expandable for hierarchical items? (PyQT5)
body: <p>I have a some dictionary variables such as :</p>
  
  <pre><code>{"Courses" : ["Math" , "Science" , "English"]} , 
  {"Cars" : ["Ford" , "BMW" , "Mercedes"]} , etc.
  </code></pre>
  
  <p>When I get the selected value of the QCombobox, I lose the key to which it applies!</p>