fact: Definition extendable_equiv (n : nat) {A B : Type} (C : B -> Type) (f : A -> B) `{IsEquiv _ _ f} : ExtendableAlong n f C.
imports: HoTT.Basics HoTT.Types Equiv.PathSplit PathAny Cubical.DPath Cubical.DPathSquare Colimits.Coeq Colimits.MappingCylinder