∀ {k G : Type u} [inst : CommRing k] [inst_1 : Group G] {A B C : Rep k G} (φ : A ⟶ B) (ψ : B ⟶ C) (n : ℕ),
  groupCohomology.map (MonoidHom.id G) (CategoryTheory.CategoryStruct.comp φ ψ) n =
    CategoryTheory.CategoryStruct.comp (groupCohomology.map (MonoidHom.id G) φ n)
      (groupCohomology.map (MonoidHom.id G) ψ n)