,[0.7, -0.9]])
    >>> q = np.eye(2)
    >>> x = linalg.solve_discrete_lyapunov(a, q)
    >>> x
    array([[ 0.70872893,  1.43518822],
           [ 1.43518822, -2.4266315 ]])
    >>> np.allclose(a.dot(x).dot(a.T)-x, -q)
    True

    Nr