title: HowTo restore QTreeView last expanded state?
body: <p>What I have:</p>
  
  <ol>
  <li><code>QTreeView</code> class with table data</li>
  <li>And connected <code>QAbstractTableModel</code> model</li>
  </ol>
  
  <p><strong>Question</strong>: how to save expanded state of items? Is some one have finished solutions? </p>
  
  <p>PS: I know, that I can do this code by myself, but I don't have much time, and this is not the major problem of our project, but still we need it, because app contain a lot of such tables, and every time expanding tree items is annoyed process...</p>