`{Funext} (n : nat) {A B : Type} {C : B -> Type} {f : A -> B} : ExtendableAlong n.+2 f C -> IsEquiv (fun g => g oD f) := isequiv_pathsplit n o (equiv_extendable_pathsplit n.+2 C f). Global Instance ishprop_extendable `{Funext} (n : nat) {A B : Type} (C : B -> Type) (f : A -> B) : IsHProp (ExtendableAlong n.+2 f C). Proof. exact (istrunc_equiv_istrunc _ (equiv_extendable_pathsplit n.+2 C f)^-1). Defined.
Require Import HoTT.Basics HoTT.Types. Require Import Equiv.PathSplit Homotopy.IdentitySystems. Require Import Cubical.DPath Cubical.DPathSquare. Require Import Colimits.Coeq Colimits.MappingCylinder.