def test_type(self):
        rset = event.ResultSet()
        with pytest.raises(NotImplementedError):
            rset.extend([])
        with pytest.raises(NotImplementedError):
            rset.extend(False)
def test_impl(df):
            B = df.A.str.split(',')
            df2 = pd.DataFrame({'B': B})
            return df2[df2.B.str.len() > 1]