title: How to hide QComboBox items instead of clearing them out
body: <p>I can't find a way to hide <code>QComboBox</code> items. So far the only way to filter its items out is to delete the existing ones (with <code>.clear()</code> method). And then to rebuild the entire <code>QComboBox</code> again using its <code>.addItem()</code> method.</p>
  
  <p>I would rather temporary hide the items. And when they are needed to unhide them back.
  Is hide/unhide on QCombobox items could be accomplished?</p>