[Kwant] scatter without a center area

Hi, I want to calculate conductance between two different leads. This is what I have tried: 1. build an empty center area. This does not work because kwant doesn't know how to attach leads to an empty area. 2. use lead_1.attach_lead(lead_2). Kwant.plot does not correctly plot two leads, so I suppose it doesn't work. I don't want to build a center area that is the same with one of the leads, because my system is very large and I suppose this will be time-consuming. Best! Chong Wang Ph. D. candidate Institute of Advanced Study, Tsinghua University, Beijing 100084