def arma_acf(ar, ma, nobs=10):
    '''theoretical autocorrelation function of an ARMA process

    Parameters
    ----------
    ar : array_like, 1d
        coefficient for autoregressive lag polynomial, including zero lag
    ma : array_like, 1d
        coefficient for moving-average lag polynomial, including zero lag
    nobs : int
        number of terms (lags plus zero lag) to include in returned acf

    Returns
    -------
    acf : array
        autocorrelation of ARMA process given by ar, ma


    See Also
    --------
    arma_acovf
    acf
    acovf

    '''
    acovf = arma_acovf(ar, ma, nobs)
    return acovf[0]/acovf
dataset/ETHPy150Open statsmodels/statsmodels/statsmodels/tsa/arima_process.py/arma_acf/swapped operands of `/`