[Kwant] Re: 3d structure model and add 3d leads

Hi Yue, Take a look at the full traceback. Above you'll see the original error: "Builder does not interrupt the lead, this lead cannot be attached." In order for it to be possible to attach a lead to a system, the system must interrupt the lead cross-section. For that you need to add more sites to the system, for example by changing its shape function.