Reinsert the hidden items.

def _reatach(self):
        """Reinsert the hidden items."""
        for item, p, idx in self._detached:
            # The item may have been deleted.
            if self.treeview.exists(item) and self.treeview.exists(p):
                self.treeview.move(item, p, idx)
        self._detached = []