proposition: Lemma istighttightapSet {X : tightapSet} : ∏ x y : X, ¬ (x ≠ y) -> x = y.
proof: Proof. exact (pr2 (pr2 (pr2 X))). Qed.
imports: UniMath.Algebra.BinaryOperations UniMath.Foundations.Propositions UniMath.MoreFoundations.Sets UniMath.MoreFoundations.Tactics UniMath.MoreFoundations.DecidablePropositions