def test_type(self):
        rset = event.ResultSet()
        with pytest.raises(NotImplementedError):
            rset.extend([])
        with pytest.raises(NotImplementedError):
            rset.extend(False)
def _update_width(self, width_diff):
    if self._items_total_width is None:
      self._items_total_width = self.get_allocation().width