def METHOD_NAME(self):
    nc = 4
    n = 10
    shape = [nc, n]
    mps = np.ones(shape, dtype=complex)
    mps /= np.linalg.norm(mps, axis=0, keepdims=True)
    coord = sp.randn([n, 1], dtype=float)
    A = linop.Sense(mps, coord=coord)
    F = sp.linop.FFT([n])
    p_expected = np.zeros(n, complex)
    for i in range(n):
        x = np.zeros(n, complex)
        x[i] = 1.0
        p_expected[i] = 1 / F(A.H(A(F.H(x))))[i]
    p = precond.circulant_precond(mps, coord=coord)
    npt.assert_allclose(p, p_expected, atol=1e-1, rtol=1e-1)