fact: Definition ooextendable_isnull_fibers {A B} (f : A -> B) (C : B -> Type) : (forall b, ooExtendableAlong (const_tt (hfiber f b)) (fun _ => C b)) -> ooExtendableAlong f C := fun null n => extendable_isnull_fibers n f C null.
imports: HoTT.Basics HoTT.Types Extensions NullHomotopy Modality