∀ {k G H : Type u} [inst : CommRing k] [inst_1 : Group G] [inst_2 : Group H] {A : Rep k H} {B : Rep k G} (f : G →* H)
  (φ : (Action.res (ModuleCat k) f).obj A ⟶ B),
  Function.Injective ⇑f → ∀ [CategoryTheory.Epi φ] (i : ℕ), CategoryTheory.Epi ((groupCohomology.cochainsMap f φ).f i)