def test_bool(self):
        prio_set_list = event._PrioritizedSetList()

        assert bool(prio_set_list) is False

        prio_set_list.add(0, None)
        assert bool(prio_set_list) is True
def add_item(self, item_value=None, index=None):
    if item_value is None:
      item_value = self._new_item_default_value