{A B} {Q : B -> Type} (f : A -> B) (C : sig Q -> Type) := forall n, HomotopyExtendableAlong n f C.
Require Import HoTT.Basics HoTT.Types. Require Import Equiv.PathSplit Homotopy.IdentitySystems. Require Import Cubical.DPath Cubical.DPathSquare. Require Import Colimits.Coeq Colimits.MappingCylinder.