def corofunc1():
            called[0] += 1
            return event.ReturnValue(insert_events=[evt2], append_events=[evt])
def test_impl(n):
            S1 = pd.Series(np.ones(n))
            S2 = pd.Series(np.random.ranf(n))
            df = pd.DataFrame({'A': S1, 'B': S2})
            return df.A.sum()