title: Remove item from QTreeView without QModelIndex
body: <p>let's say I decide to randomly remove a few items from my model. I have the references to those items but that's not enough to call the <strong>beginRemoveRows()</strong> method properly. It needs to know the QModelIndex for each item.</p>
  
  <p>But to get the QModelIndex for an item, I need to know the QModelIndex for the parent as well! </p>
  
  <pre><code>virtual QModelIndex     index(int row, int column, const QModelIndex &amp; parent = QModelIndex()) 
  </code></pre>
  
  <p>Only the RootItem doesn't have a parent and therefore doesn't need a QModelIndex. So I would need to start from there and recursively traverse through all children until I end up with the appropriate QModelIndex for each item if this is the correct way of doing things.</p>
  
  <p>Is there a better way to get the QModelIndex for a random item?</p>