fact: Definition cancelL_isequiv {A B C} (g : B -> C) {f : A -> B} `{IsEquiv B C g} `{IsEquiv A C (g o f)} : IsEquiv f := isequiv_homotopic (g^-1 o (g o f)) (fun a => eissect g (f a)).
imports: Basics.Overture Basics.PathGroupoids Basics.Contractible Basics.Tactics