Definition PreShv_to_slice_ob_nat {X Y : PreShv ∫P} (f : X --> Y) (c : C) : (∑ Px : ## P c, ## X (c,, Px)) → (∑ Px : ## P c, ## Y (c,, Px)) := λ p, pr1 p ,, (pr1 f) (c ,, (pr1 p)) (pr2 p).
Require Import UniMath.Foundations.Sets. Require Import UniMath.MoreFoundations.Tactics. Require Import UniMath.CategoryTheory.Core.Categories. Require Import UniMath.CategoryTheory.Core.Isos. Require Import UniMath.CategoryTheory.Core.Functors. Require Import UniMath.CategoryTheory.Core.NaturalTransformations. Require Import UniMath.CategoryTheory.FunctorCategory. Require Import