'Test firwin2 for calculating Type III filters'

def test06(self):

    ntaps = 1501
    freq = [0.0, 0.5, 0.55, 1.0]
    gain = [0.0, 0.5, 0.0, 0.0]
    taps = firwin2(ntaps, freq, gain, window=None, antisymmetric=True)
    assert_equal(taps[(ntaps // 2)], 0.0)
    assert_array_almost_equal(taps[:(ntaps // 2)], (- taps[((ntaps // 2) + 1):][::(-1)]))
    (freqs, response1) = freqz(taps, worN=2048)
    response2 = np.interp((freqs / np.pi), freq, gain)
    assert_array_almost_equal(abs(response1), response2, decimal=3)
