fact: Definition extension_factsys {A B : Type} (f : A -> B) {c1f : class1 factsys f} (P : B -> Type) (c2P : class2 factsys (@pr1 B P)) (d : forall a:A, P (f a)) : ExtensionAlong f P d.
imports: HoTT.Basics HoTT.Types Extensions PathAny