def _get_fut_stats(series, window_width):
    """
    Helper function for `predict` that calculates statistics
    for the future dataset

    Parameters
    ----------
    series : pd.Series, shape (n_samples, )
        Samples
    window_width: int
        The size of the rolling window.

    Returns
    -------
    fut_mean : pd.Series, shape (n_samples, )
        Mean calculated using the moving window for each day of the future
        model.
    fut_std : pd.Series, shape (n_samples, )
        Standard deviation calculated using the moving window for each day of
        the future model.
    fut_zscore: pd.Series, shape (n_samples, )
        Z-Score coefficient calculated by comparing the series values, the
        means, and standared deviations.
    """
    fut_mean = series.rolling(window_width, center=True).mean()
    fut_std = series.rolling(window_width, center=True).std()
    fut_zscore = (series - fut_mean) / fut_std
    return fut_mean, fut_std, fut_zscore