Mixing thermal scattering librarries

Hey, would it be possible to be able to “mix” thermal scattering data? Conceptually something like this:

`w30 = (porosity - 0.10) / (0.30 - 0.10)`

w10 = 1.0 - w30

# Add both thermal kernels with fractions that sum to 1.0
graphite.add_s_alpha_beta('c_Graphite_10p', fraction=w10)
graphite.add_s_alpha_beta('c_Graphite_30p', fraction=w30)

This also demonstrates the use case.