def test_nabsH(self):
        H = ([1, 2], [2, 0, .25], 1)
        N = 129
        w = np.linspace(0, 2*np.pi, num=N, endpoint=True)
        z = np.exp(1j*w)
        r1 = -np.abs(ds.evalTF(H, z))
        r2 = ds.nabsH(w, H)
        self.assertTrue(np.allclose(r1, r2, atol=1e-8, rtol=1e-5))
takes a an iterator and returns an iterator over iterators,
dataset/ETHPy150Open ggventurini/python-deltasigma/deltasigma/tests/test_nabsH.py/TestNabsH.test_nabsH--crossover with--dataset/ETHPy150Open CGATOxford/cgat/CGAT/GFF3.py/chrom_iterator