fact: Definition extension_functor_sigma_id {A} {P Q : A -> Type} (f : forall a, P a -> Q a) (C : sig Q -> Type) (ef : forall a, ExtendableAlong 1 (f a) (fun v => C (a;v))) (s : forall z, C (functor_sigma idmap f z)) : ExtensionAlong (functor_sigma idmap f) C s.
imports: HoTT.Basics HoTT.Types Equiv.PathSplit PathAny Cubical.DPath Cubical.DPathSquare Colimits.Coeq Colimits.MappingCylinder