∀ {α : Type u_1} {m : MeasurableSpace α} (f g : MeasureTheory.SimpleFunc α ENNReal),
  { toFun := (f + g).lintegral, map_add' := ⋯, map_smul' := ⋯ } =
    { toFun := f.lintegral, map_add' := ⋯, map_smul' := ⋯ } + { toFun := g.lintegral, map_add' := ⋯, map_smul' := ⋯ }