∀ {k G : Type u} [inst : CommRing k] [inst_1 : Group G] {A B : Rep.{u, u, u} k G} (φ : A ⟶ B) [CategoryTheory.Mono φ]
  (i : ℕ), CategoryTheory.Mono ((groupCohomology.cochainsMap (MonoidHom.id G) φ).f i)