fact: Definition invstruct_free_gr (X : hSet) : invstruct (@op (free_gr' X)) (pr2 (free_gr' X)).
imports: UniMath.MoreFoundations.Subtypes UniMath.MoreFoundations.Sets UniMath.Algebra.Monoids UniMath.Algebra.Groups UniMath.Algebra.IteratedBinaryOperations UniMath.Combinatorics.Lists