def serialized(self):
        to_ret = {}
        for group, requirements in self.items():
            to_ret[group] = [str(requirement) for requirement in requirements]
        return to_ret
def test_impl(n):
            df = pd.DataFrame({'A': np.arange(n)})
            df['B'] = df.A.map(lambda a: 2 * a)
            return df.B.sum()