[Kwant] Making a 1D Quantum Wire

Hey, I have been trying to set up a 1D quantum wire and then calculate the conductance. However when trying to calculate the smatrix it gives me the following error: ValueError: Input needs to be a square matrix. And my system that I am working with is defined as follows: lat = kwant.lattice.chain(a) How can I possibly resolve this problem? Or where should I be looking to get an idea? Sincerely, Binayyak