proposition: Lemma eq_sym_invol {A} (x y : A) (e : x = y) : e^^ = e.
proof: Proof. destruct e. reflexivity. Defined.
imports: Coq.Program.Tactics Equations.Init Equations.Signature Equations.CoreTactics Equations.HoTT.Logic Equations.HoTT.Classes Equations.HoTT.EqDec