Hello Kwant users, I am trying to compare the retarded Green's function of a simple 1D wire attached to two leads using two different methods: (I) Using scattering wave function obtained from the Kwant software and using Eq. 25 in energy domain of "Numerical simulations of time resolved quantum electronics (https://arxiv.org/abs/1307.6419) written by Kwant authors. (II) Direct computation of the retarded Green's function by inverting device Hamiltonian with self energies of the attached leads (again computed from the Kwant software): G^r(E) = [E+\i*\eta - H- \Sigma^r_{leads}]^{-1} for a relatively small system size (5 sites in the attached example). Here both H and \Sigma^r are computed from the Kwant software. However, I find that these two results do not agree even in a simple 1D example when on-site potential is present in the few sites of device or scattering region only. I have attached the Python script with this email. Does anyone know the reason behind the discrepancy between the two methods?I would greatly appreciate any comments/suggestions on how we can resolve this error? Thanks!