`{Funext} {A B : Type} (C : B -> Type) (f : A -> B) : ooExtendableAlong f C -> IsEquiv (fun g => g oD f) := fun ps => isequiv_extendable 0 (fst (ps 1%nat), snd (ps 2)).
Require Import HoTT.Basics HoTT.Types. Require Import Equiv.PathSplit Homotopy.IdentitySystems. Require Import Cubical.DPath Cubical.DPathSquare. Require Import Colimits.Coeq Colimits.MappingCylinder.