[Kwant] Graphene sheet with 4-atom rectangular unitcell

[Masoumeh Alihosseini via Kwant-discuss]

Hi dear all,
I have a question, I want to work with rectangular graphene cell with 4 atoms 
in the unitcell. Like zigzag nanoribbon but I want to apply periodicity in y 
direction for both scattering region and leads. Could you please help me?
Thank you,
Masoumeh