{X Y : Type} (f : X -> Y) `{feq : IsEquiv _ _ f} : RetractOf X -> RetractOf Y. Proof. intros [A r s H]; refine (Build_RetractOf Y A (r o f^-1) (f o s) _); intros x. exact (ap r (eissect f (s x)) @ H x). Defined.
Require Import HoTT.Basics HoTT.Types. Require Import HFiber Constant. Require Import Truncations.Core Modalities.Modality. Require Import Homotopy.IdentitySystems.