def save(self, filename=None):
        filename = Path(filename) if filename is not None else self.filename
        with filename.open("w") as f:
            f.write(self.yaml)
def test_impl(n):
            df = pd.DataFrame({'A': np.ones(n), 'B': np.random.ranf(n)})
            df['moving average'] = df.A.rolling(window=5, center=True).mean()
            return df['moving average'].sum()