`{Funext} {A B : Type} (C : B -> Type) (f : A -> B) : ooExtendableAlong f C <~> IsEquiv (fun (g : forall b, C b) => g oD f) := equiv_oopathsplit_isequiv _ oE equiv_ooextendable_pathsplit _ _.
Require Import HoTT.Basics HoTT.Types. Require Import Equiv.PathSplit Homotopy.IdentitySystems. Require Import Cubical.DPath Cubical.DPathSquare. Require Import Colimits.Coeq Colimits.MappingCylinder.