∀ {α : Type u_1} {m : MeasurableSpace α} (s : MeasureTheory.SignedMeasure α) (μ : MeasureTheory.Measure α),
  (s.toJordanDecomposition.posPart.singularPart μ).MutuallySingular (s.toJordanDecomposition.negPart.singularPart μ)