{A B C D} {g : C -> D} {k : B -> D} (f h : A -> Pullback k g) (p1 : pullback_pr1 o f == pullback_pr1 o h) (p2 : pullback_pr2 o f == pullback_pr2 o h) (q : forall a, (ap k) (p1 a) @ (h a).2.2 = (f a).2.2 @ (ap g) (p2 a)) : f == h. Proof. intro a. apply equiv_path_pullback. exists (p1 a). exists (p2 a). apply sq_path, q. Defined.
Require Import HoTT.Basics HoTT.Types. Require Import HFiber Homotopy.IdentitySystems Cubical.PathSquare. Require Import Diagrams.CommutativeSquares.