title: Value in MainWindow returned from childWindow
body: <p>How do I send a value from a ChildWindow to a MainWindow once the ChildWindow is closed?.</p>
  
  <p>When the "closeButton" in ChildWindow is pressed, ChildWindow sends the calculated value to MainWindow.</p>
  
  <p>I did a test like this:</p>
  
  <pre><code>def closeEvent(self, evnt):
          value = 34
          return value
  </code></pre>
  
  <p>And it didn't work, I got this:</p>
  
  <pre><code>TypeError: invalid result type from ChildWindow.closeEvent()
  </code></pre>