, ab=None, axis=-1):
    &#34;&#34;&#34;Yulewalk filter.

    Parameters
    ----------
    X : array, shape = (n_channels, n_samples)
        Data to filter.
    sfreq : float
        Sampling frequency.
    zi : array, shape=(n_channels, filter_order)
        Initial conditions.
    a, b : 2-tuple | None
        Coefficients of an IIR filter that is used to shape the spectrum of
        the signal when calculating artifact statistics. The output signal
        does not go through this filter. This is an o