Hm, not exactly sure why we removed that tutorial... Anyway, the script was not published in the tutorial, so it wouldn't help.
Actually it's very simple. Assuming you have all transmission spectra, one for each bias, in one NC file, just do:
all_t = nlread('file.nc', TransmissionSpectrum)
energies = all_t[0].energies().inUnitsOf(eV)
bias = []
data = []
for t in all_t:
bias.append(t.bias().inUnitsOf(Volt))
data.append(t.evaluate())
import pylab
pylab.figure()
pylab.xlabel('Energy (eV)',fontsize=12,family='sans-serif')
pylab.ylabel('Bias (V)',fontsize=12,family='sans-serif')
pylab.title('Transmission spectrum as function of bias')
pylab.contourf(energies,bias,data,40,cmap=pylab.cm.jet)
pylab.colorbar()
pylab.show()