- To use DirectSum, you first need to load the SYM Package using Needs["SYM`"].

- The
*ideal*can be any symbol. Specifically, in the context of the theory of Lie algebras, they can be lists of differential operators representing a base which spans a Lie algebra, semi-direct sums of ideals or, using the symbolic representation of a Lie Algebra included in the Lie Algebra's database._{i}