fact: Definition isequiv_isequiv_postcompose {A B : Type} (f : A -> B) (postcomp := (fun (C : Type) (h : C -> A) => f o h)) (Aeq : IsEquiv (postcomp A)) (Beq : IsEquiv (postcomp B)) : IsEquiv f.
imports: Basics.Overture Basics.PathGroupoids Basics.Contractible Basics.Tactics