{A B C D} {f : A -> B} {g : C -> D} {h : A -> C} {k : B -> D} (p : k o f == g o h) := IsEquiv (pullback_corec p).
Require Import HoTT.Basics HoTT.Types. Require Import HFiber Homotopy.IdentitySystems Cubical.PathSquare. Require Import Diagrams.CommutativeSquares.