[Kwant] About cubic lattice hopping

hello ! I am trying to simulate a cubic lattice and I want to write hopping without using neighbors() function,as I am writing different hopping parameters in different directions my lattice is this: lat = kwant.lattice.general([(1,0,0),(0,1,0),(0,0,1)],[(0,0,0)]) def make(a = 4 ,b = 5, c= 1,t=1,delta = 1): def cube(pos): x,y,z = pos return 0<=x<=a and 0<=y<=b and 0<=z<=c sys = kwant.Builder() sys[lat.shape(cube,(0,0,0))] = -4* t sys[lat(0,0,0),lat(0,0,1)] = -t return sys this code is showing me an error: TypeError: 'Polyatomic' object is not callable