def __init__(self, name, host='127.0.0.1', port=27017):
        self.name = name
        self.host = host
        self.port = port
def test_impl(n):
            df = pd.DataFrame({'A': np.arange(n), 'B': np.random.ranf(n)})
            Ac = df.A.rolling(3).sum()
            return Ac.sum()