∀ {α : Type u_1} {β : Type u_2} [inst : PseudoMetricSpace α] [inst_1 : MeasurableSpace α] [OpensMeasurableSpace α]
  [inst_3 : MeasurableSpace β] [SecondCountableTopology α] {f g : β → α},
  Measurable f → Measurable g → Measurable fun b => dist (f b) (g b)