[Kwant] Re: superurrent operator in Kwant

[mohit . gupta9607]

Dear Abbout,
Thank you for your helpful reply it clears up a lot. I tried to obtain H12 as 
you mentioned:
H12=syst.hamiltonian_submatrix(to_sites=Sites1, from_sites=Sites2)
But it gives me the error that "an integer is required".
Although that is not a major issue I could try to construct H12 manually. 
Thanks a lot for your help.