title: How to only allow certain items to be multiple selected in a QTableWidget?
body: <p>I have a QTableWidget and want items to be selectable depending on what's already selected (only if they have the same content in second column).</p>
  
  <p>I know how to make items selectable or not. But everything should remain selectable so the user can select a single item to start the selection fresh. Only adding to a selection by keeping shift or ctrl pressed should allow/select only suitable items.</p>
  
  <p>Where can I hook into to make adding to a selection only accept suitable rows?</p>
  
  <p>Note: I'm using PySide but I can work from C++ or PyQt code just fine.</p>