human
I am working on the file "2.3.transport_through_barrier.ipynb".
The first task is:
The function below is almost like make_wire_with_flat_potential.  The difference is that it can be tuned to use a general potential using its first parameter.
Can you write Python program for it?

Can you provide a the Python program you requested?
assistant
#Here is the Python program you requested.

def make_barrier(pot, W=40, L=70, t=1):
    def onsite(*args):
        return 4 * t - pot(*args)

    # Construct the scattering region.
    sr = kwant.Builder()
    sr[(lat(x, y) for x in range(L) for y in range(W))] = onsite
    sr[lat.neighbors()] = -t

    # Build and attach lead from both sides.
    lead = make_lead_x(W, t)
    sr.attach_lead(lead)
    sr.attach_lead(lead.reversed())

    return sr