@@ -47,7 +47,7 @@ def make_system(R):

 def main():

     syst = make_system(100)

-    print(kwant.smatrix(syst, 1.1, [0.1]).transmission(0, 1))

+    print(kwant.smatrix(syst, 1.1, params=dict(B=0.1)).transmission(0, 1))

 if __name__ == '__main__':

@@ -16,7 +16,9 @@ class Lead:

         self.t = t

         self.potential = potential

-    def selfenergy(self, fermi_energy, args=()):

+    def selfenergy(self, fermi_energy, args=(), params=None):

+        assert not args

+        assert params is None

         return square_selfenergy(self.width, self.t,

                                  self.potential + fermi_energy)

@@ -73,8 +75,10 @@ class System(kwant.system.FiniteSystem):

         self.leads = [Lead(shape[1], hopping, lead_potentials[i])

                       for i in range(2)]

-    def hamiltonian(self, i, j):

+    def hamiltonian(self, i, j, *args, params=None):

         """Return an submatrix of the tight-binding Hamiltonian."""

+        assert not args

+        assert params is None

         if i == j:

             # An on-site Hamiltonian has been requested.

             result = 4 * self.t + self.pot(self.pos_from_nodeid(i))