Expand \((v_n - \theta)^l\)
l (int) – power of \((v_n - \theta)\)
poly with attribute keyfor = (‘e^{-knh}IE_n’, ‘e^{-knh}IEZ_n’, ‘e^{-kh}’, ‘v_{n-1}-theta’, ‘sigma_v’)
keyfor
Poly