cyl_extendable' (n : nat) {A B} (f : A -> B) (C : B -> Type) (ext : ExtendableAlong n f C) : ExtendableAlong n cyl (C o (pr_cyl' f)). Proof. rapply cyl_extendable. refine (cancelL_extendable n C cyl pr_cyl _ ext). rapply extendable_equiv. 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.