sed to obtain the impulse
    response of the filter. Finally, the numerator polynomial is obtained by a
    least squares fit to this impulse response. For a more detailed
    explanation of the algorithm see [1]_.

    Parameters
    ----------
    order : int
        Filter order.
    F : array
        Normalised frequency breakpoints for the filter. The frequencies in F
        must be between 0.0 and 1.0, with 1.0 corresponding to half the sample
        rate. They must be in increasing order and start