_zpk, bilinear
lp2bs

Notes
-----
This is derived from the s-plane substitution

.. math:: s \rightarrow \frac{s \cdot \mathrm{BW}}{s^2 + {\omega_0}^2}

This is the "wideband" transformation, producing a stopband with
geometric (log frequency) symmetry about `wo`.

.. versionadded:: 1.1.0

Examples
--------
Transform a low-pass filter represented in 'zpk' (Zero-Pole-Gain) form
into a bandstop filter represented in 'zpk' form, with a center frequency wo and
bandwidth bw.

>>> from scipy.signal import lp2bs_zpk
>>> z   = [             ]
>>> p   = [ 0.7 ,    -1 ]
>>> k   = 9
>>> wo  = 0.5
>>> bw  = 10
>>> lp2bs_zpk(z, p, k, wo, bw)
(   array([0.+0.5j, 0.+0.5j, 0.-0.5j, 0.-0.5j]),
    array([14.2681928 +0.j, -0.02506281+0.j,  0.01752149+0.j, -9.97493719+0.j]),
    -12.857142857142858)
rp