fact: Definition extendable_functor_sum (n : nat) {A B A' B'} (f : A -> A') (g : B -> B') (P : A' + B' -> Type) (ef : ExtendableAlong n f (P o inl)) (eg : ExtendableAlong n g (P o inr)) : ExtendableAlong n (functor_sum f g) P.
imports: HoTT.Basics HoTT.Types Equiv.PathSplit PathAny Cubical.DPath Cubical.DPathSquare Colimits.Coeq Colimits.MappingCylinder