title: Get selected QTreeWidget cells
body: <p>Say I have a treeWidget with 6 rows and 6 columns. I have set the selection behaviour to select individual items as opposed to the entire row. This works as expected and I can select individual cells. My question is how do I query what cells are currently selected?</p>
  
  <p>I've tried using treeWidget.selectedItems(), but this returns a list treeWidgetItems, which from what I can tell, corresponds to the whole row. So if I select several columns in the same row, this command returns a list  containing a single treeWidgetItem. And I can find no way to find out which columns are selected within that treeWidgetItem.</p>
  
  <p>Any ideas how to go about this?</p>