def test_order(self):
        assert (event.Priority.PRE_CORE
                > event.Priority.CORE
                > event.Priority.POST_CORE
                > event.Priority.PRE_DEFAULT
                > event.Priority.DEFAULT
                > event.Priority.POST_DEFAULT)
def test_impl(n):
            df = pd.DataFrame({'A': np.arange(n) + 1.0, 'B': np.random.ranf(n)})
            Ac = df.A.pct_change(1)
            return Ac.sum()