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