def test_type(self):
        rset = event.ResultSet()
        with pytest.raises(NotImplementedError):
            rset.extend([])
        with pytest.raises(NotImplementedError):
            rset.extend(False)
def test_impl(n):
            df = pd.DataFrame({'A': ['aa', 'bb', 'aa', 'cc', 'cc']})
            return df.A.nunique()