fact: Definition bool_varspec := make_varspec bool_signature natset (λ _, bool_sort).
imports: UniMath.MoreFoundations.Notations UniMath.MoreFoundations.Bool UniMath.Combinatorics.StandardFiniteSets UniMath.Combinatorics.MoreLists UniMath.Algebra.Universal.Algebras UniMath.Algebra.Universal.VTerms