∀ {α : Type u_1} {F : Type u_2} {p : ENNReal} [inst : NormedAddCommGroup F] {m m0 : MeasurableSpace α}
  {μ : MeasureTheory.Measure α} (hm : m ≤ m0) (f g : ↥(MeasureTheory.lpMeasSubgroup F m p μ)),
  MeasureTheory.lpMeasSubgroupToLpTrim F p μ hm (f + g) =
    MeasureTheory.lpMeasSubgroupToLpTrim F p μ hm f + MeasureTheory.lpMeasSubgroupToLpTrim F p μ hm g