∀ {α : Type u_1} {m : MeasurableSpace α} {μ : MeasureTheory.Measure α} {t : MeasureTheory.SignedMeasure α} {f : α → ℝ},
  MeasureTheory.Integrable f μ →
    MeasureTheory.IsFiniteMeasure (t.toJordanDecomposition.negPart + μ.withDensity fun x => ENNReal.ofReal (-f x))