fact: Definition isequiv_commsq {A B C D} (f : A -> B) (g : C -> D) (h : A -> C) (k : B -> D) (p : k o f == g o h) `{IsEquiv _ _ f} `{IsEquiv _ _ h} `{IsEquiv _ _ k} : IsEquiv g.
imports: Basics.Overture Basics.PathGroupoids Basics.Contractible Basics.Tactics