Take derivative of each term
key (tuple) – key corresponding to a term, i.e., (i,(n1,m1),(n2,m2),…,(nj,mj)) which stands for \((\lambda h)^{i} M^{(n_1)m_1}(s) ... M^{(n_l)m_l}(s)\).
coef (Fraction) – corresponding coefficient.
poly representing the derivative.
Poly