def METHOD_NAME(k_vars, ar):
    '''create autoregressive correlation matrix
    This might be MA, not AR, process if used for residual process - check
    Parameters
    ----------
    ar : array_like, 1d
        AR lag-polynomial including 1 for lag 0
    '''
    from scipy.linalg import toeplitz
    if len(ar) < k_vars:
        ar_ = np.zeros(k_vars)
        ar_[:len(ar)] = ar
        ar = ar_
    return toeplitz(ar)