fact: Definition equiv_sigma_pullback : {p : Pullback f g & Pullback (transport A p.2.2 o r p.1) (s p.2.1)} <~> Pullback (functor_sigma f r) (functor_sigma g s).
imports: HoTT.Basics HoTT.Types HFiber PathAny Cubical.PathSquare Diagrams.CommutativeSquares