xa yb (p : xa = yb) : PreCategoryOfStructures.f (idtoiso (precategory_of_structures P) p : morphism _ _ _) = idtoiso X p..1. Proof. induction p; reflexivity. Defined.
Require Import Category.Core Category.Univalent Category.Morphisms. Require Import Structure.Core. Require Import Types.Sigma Trunc Equivalences. Require Import Basics.Iff Basics.Tactics.