∀ {ι : Type u_1} {M : Type u_2} {σ : Type u_3} [inst : DecidableEq ι] [inst_1 : AddCommMonoid M] [inst_2 : SetLike σ M]
  [inst_3 : AddSubmonoidClass σ M] (ℳ : ι → σ) (h : DirectSum.IsInternal ℳ),
  Function.LeftInverse (Equiv.ofBijective (⇑(DirectSum.coeAddMonoidHom ℳ)) h).invFun
    (Equiv.ofBijective (⇑(DirectSum.coeAddMonoidHom ℳ)) h).toFun