def test_order(self):
        assert (event.Priority.PRE_CORE
                > event.Priority.CORE
                > event.Priority.POST_CORE
                > event.Priority.PRE_DEFAULT
                > event.Priority.DEFAULT
                > event.Priority.POST_DEFAULT)
def _update_height(self, height_diff):
    if self._items_total_height is None:
      self._items_total_height = self.get_allocation().height