fact: Definition cyl_extendable (n : nat) {A B} (f : A -> B) (C : Cyl f -> Type) (ext : ExtendableAlong n cyl C) : ExtendableAlong n cyl C.
imports: HoTT.Basics HoTT.Types Equiv.PathSplit PathAny Cubical.DPath Cubical.DPathSquare Colimits.Coeq Colimits.MappingCylinder