[Kwant] the phase of wave functions

Hello all, My question is about modifying the phase of wave functions. I want to calculate derivative of scattering matrix with respect to energy and they come out to be discontinuous because of the phases. To remedy this I need to modify these phases. Following the suggestion of Anton Akhmerov in this mail group I understood how to modify the phase of modes in the leads. But I also need to change the phase of wave functions in the scattering region to obtain continuous scattering matrices at different energies. I wonder if there is an another way to call wave functions in the scattering region (apart from kwant.solvers.default.wave_function) or a method to modify these phases. Thank you in advance. Nur