def _last_index(self, s):
        self.set_index(max(0, self._find_one_after_last_labeled_index() - 1))
def test_impl():
            A = StringArray(['ABC', 'BB', 'ADEF'])
            df = pd.DataFrame({'A': A})
            B = df.A.str.contains('AB*', regex=True)
            return B.sum()