proposition: Lemma isaprop_has_β (L : lambda_theory) : isaprop (has_β L).
proof: Proof. do 2 (apply impred; intro). apply setproperty. Qed.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.Combinatorics.StandardFiniteSets UniMath.Combinatorics.Tuples UniMath.AlgebraicTheories.AlgebraicTheories UniMath.AlgebraicTheories.LambdaTheoryCategoryCore