proposition: Lemma free_gr_hrel_in_rev {X : hSet} (x : X ⨿ X) : free_gr_hrel X (coprodcomm X X x::x::[]) [].
proof: Proof. pose (H := free_gr_hrel_in (coprodcomm X X x)). rewrite coprodcomm_coprodcomm in H. exact H. Defined.
imports: UniMath.MoreFoundations.Subtypes UniMath.MoreFoundations.Sets UniMath.Algebra.Monoids UniMath.Algebra.Groups UniMath.Algebra.IteratedBinaryOperations UniMath.Combinatorics.Lists