title: how to create folder view in pygtk inside main window
body: <p>I'm trying to implement a folder viewer to view the structure of a specific path. and this folder view should look like a the tree widget in PyGtk , I used file dialog, but it doesn't expand down. Can anyone help? The figure below describes the idea of what I want to do.</p>
  
  <p><a href="https://i.stack.imgur.com/8oTf6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8oTf6.png" alt="enter image description here"></a></p>