∀ {J : Type v} [inst : CategoryTheory.SmallCategory J] [inst_1 : CategoryTheory.IsFiltered J]
  (F : CategoryTheory.Functor J AddGrpCat),
  AddGrpCat.FilteredColimits.G F =
    AddMonCat.FilteredColimits.colimit (F.comp (CategoryTheory.forget₂ AddGrpCat AddMonCat))