proposition: Lemma Side_eqP : Equality.axiom Side_eq.
proof: Proof. by case; case; constructor. Qed.
imports: Coq(ssreflect ssrbool ssrfun Eqdep) mathcomp(ssrnat seq eqtype choice fintype) pcm(options axioms) Coq(Classes.Morphisms Program.Basics Program.Tactics) Coq(Relations)