∀ {k G H : Type u} [inst : CommRing k] [inst_1 : Group G] [inst_2 : Group H] {A : Rep k G} {B : Rep k H} (f : G →* H)
  (φ : A ⟶ (Action.res (ModuleCat k) f).obj B), (groupHomology.mapShortComplexH1 f φ).τ₃ = φ.hom