Automatic calculation of optimum lead boundary conditions

How to choose between adding self energy, a finite slab of the lead or a combination of the two.

• We could consider running want calculations with imaginary energies to characterize the absorption in the leads and make sure they remain below a given threshold while making sure that the energies with small velocities have no time to do any damage.

• We could also revisit this idea of monitoring the leads by having "two" leads simultaneously (ne with extra stack and the other no) to control the error in real time.