title: List all subclasses of one class
body: <p>Can I return a list of all subclasses of one class? For example:</p>
  
  <pre><code>class Mother {
  
  }
  
  class ChildFoo: Mother {
  
  }
  
  class ChildBar: Mother {
  
  }
  
  let motherSubclasses = ... // TODO
  print(motherSubclasses) // should to return [ChildFoo.self, ChildBar.self]
  </code></pre>