proposition: Lemma isaprop_isrigid (T : Tree) : isaprop (isrigid T).
proof: Proof. unfold isrigid. apply isapropiscontr. Qed.
imports: UniMath.Foundations.PartB UniMath.Foundations.Propositions UniMath.Foundations.Sets UniMath.Foundations.HLevels UniMath.Combinatorics.WellOrderedSets UniMath.Combinatorics.OrderedSets UniMath.MoreFoundations.DecidablePropositions UniMath.MoreFoundations.Propositions