def test_type(self):
        rset = event.ResultSet()
        with pytest.raises(NotImplementedError):
            rset.extend([])
        with pytest.raises(NotImplementedError):
            rset.extend(False)
def test_impl(df):
            A = df.A.str.split(',')
            B = pd.Series(list(itertools.chain(*A)))
            return B