title: How to get identation width of QTreeView from QStyle
body: <p>I have pre-existing code which has a tree view like appearance but doesn't actually use QTreeView (uses QListWidget with custom paint).      </p>
  
  <p>I am tasked to add the indentation between the parent and child objects, but I can't able to find how to get the style default indentation width from QStyle. The program has to run on a variety of os and allow to use custom stylesheets. So it's important to get this option from QStyle.</p>
  
  <p>Regards.</p>