Removes all the items from this tree widget.  This will go through
        and also destroy any XTreeWidgetItems prior to the model clearing
        its references.

def clear(self):
        """
        Removes all the items from this tree widget.  This will go through
        and also destroy any XTreeWidgetItems prior to the model clearing
        its references.
        """
        # go through and properly destroy all the items for this tree
        for item in self.traverseItems():
            if isinstance(item, XTreeWidgetItem):
                item.destroy()
        
        super(XTreeWidget, self).clear()