u = - d
The symbol - is used as notation for the negation of Lie derivations.
i1 : L = lieAlgebra{a,b} o1 = L o1 : LieAlgebra
i2 : d = lieDerivation{a a b,b b a} o2 = d o2 : LieDerivation
i3 : describe(-d) o3 = a => (a b a) b => - (b b a) map => id_L sign => 0 weight => {2, 0} source => L target => L