-- Mathlib/MeasureTheory/Integral/SetToL1.lean
theorem tendsto_setToFun_of_dominated_convergence (hT : DominatedFinMeasAdditive μ T C)
    {fs : ℕ → α → E} {f : α → E} (bound : α → ℝ)
    (fs_measurable : ∀ n, AEStronglyMeasurable (fs n) μ) (bound_integrable : Integrable bound μ)
    (h_bound : ∀ n, ∀ᵐ a ∂μ, ‖fs n a‖ ≤ bound a)
    (h_lim : ∀ᵐ a ∂μ, Tendsto (fun n => fs n a) atTop (𝓝 (f a))) :
    Tendsto (fun n => setToFun μ T hT (fs n)) atTop (𝓝 <| setToFun μ T hT f)

Proof state:
case h.e'_3.h
α : Type u_1
E : Type u_2
F : Type u_3
inst✝⁴ : NormedAddCommGroup E
inst✝³ : NormedSpace ℝ E
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace ℝ F
m : MeasurableSpace α
μ : Measure α
inst✝ : CompleteSpace F
T : Set α → E →L[ℝ] F
C : ℝ
hT : DominatedFinMeasAdditive μ T C
fs : ℕ → α → E
f : α → E
bound : α → ℝ
fs_measurable : ∀ (n : ℕ), AEStronglyMeasurable (fs n) μ
bound_integrable : Integrable bound μ
h_bound : ∀ (n : ℕ), ∀ᵐ (a : α) ∂μ, ‖fs n a‖ ≤ bound a
h_lim : ∀ᵐ (a : α) ∂μ, Tendsto (fun n => fs n a) atTop (𝓝 (f a))
f_measurable : AEStronglyMeasurable f μ
fs_int : ∀ (n : ℕ), Integrable (fs n) μ
f_int : Integrable f μ
lintegral_norm_tendsto_zero : Tendsto (fun n => (∫⁻ (a : α), ENNReal.ofReal ‖fs n a - f a‖ ∂μ).toReal) atTop (𝓝 0)
n : ℕ
⊢ ‖Integrable.toL1 (fs n) ⋯ - Integrable.toL1 f f_int‖ = (∫⁻ (a : α), ENNReal.ofReal ‖fs n a - f a‖ ∂μ).toReal

Tactic:
rw [L1.norm_def]

Result:
case h.e'_3.h
α : Type u_1
E : Type u_2
F : Type u_3
inst✝⁴ : NormedAddCommGroup E
inst✝³ : NormedSpace ℝ E
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace ℝ F
m : MeasurableSpace α
μ : Measure α
inst✝ : CompleteSpace F
T : Set α → E →L[ℝ] F
C : ℝ
hT : DominatedFinMeasAdditive μ T C
fs : ℕ → α → E
f : α → E
bound : α → ℝ
fs_measurable : ∀ (n : ℕ), AEStronglyMeasurable (fs n) μ
bound_integrable : Integrable bound μ
h_bound : ∀ (n : ℕ), ∀ᵐ (a : α) ∂μ, ‖fs n a‖ ≤ bound a
h_lim : ∀ᵐ (a : α) ∂μ, Tendsto (fun n => fs n a) atTop (𝓝 (f a))
f_measurable : AEStronglyMeasurable f μ
fs_int : ∀ (n : ℕ), Integrable (fs n) μ
f_int : Integrable f μ
lintegral_norm_tendsto_zero : Tendsto (fun n => (∫⁻ (a : α), ENNReal.ofReal ‖fs n a - f a‖ ∂μ).toReal) atTop (𝓝 0)
n : ℕ
⊢ (∫⁻ (a : α), ‖↑↑(Integrable.toL1 (fs n) ⋯ - Integrable.toL1 f f_int) a‖ₑ ∂μ).toReal =
    (∫⁻ (a : α), ENNReal.ofReal ‖fs n a - f a‖ ∂μ).toReal

Proof state:
α : Type u_1
E : Type u_2
F : Type u_3
inst✝⁴ : NormedAddCommGroup E
inst✝³ : NormedSpace ℝ E
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace ℝ F
m : MeasurableSpace α
μ : Measure α
inst✝ : CompleteSpace F
T : Set α → E →L[ℝ] F
C : ℝ
hT : DominatedFinMeasAdditive μ T C
fs : ℕ → α → E
f : α → E
bound : α → ℝ
fs_measurable : ∀ (n : ℕ), AEStronglyMeasurable (fs n) μ
bound_integrable : Integrable bound μ
h_bound : ∀ (n : ℕ), ∀ᵐ (a : α) ∂μ, ‖fs n a‖ ≤ bound a
h_lim : ∀ᵐ (a : α) ∂μ, Tendsto (fun n => fs n a) atTop (𝓝 (f a))
f_measurable : AEStronglyMeasurable f μ
fs_int : ∀ (n : ℕ), Integrable (fs n) μ
f_int : Integrable f μ
⊢ Tendsto (fun e => ‖Integrable.toL1 (fs e) ⋯ - Integrable.toL1 f f_int‖) atTop (𝓝 0)

Tactic:
have lintegral_norm_tendsto_zero :
  Tendsto (fun n => ENNReal.toReal <| ∫⁻ a, ENNReal.ofReal ‖fs n a - f a‖ ∂μ) atTop (𝓝 0) :=
  (tendsto_toReal zero_ne_top).comp
    (tendsto_lintegral_norm_of_dominated_convergence fs_measurable
      bound_integrable.hasFiniteIntegral h_bound h_lim)

Result:
α : Type u_1
E : Type u_2
F : Type u_3
inst✝⁴ : NormedAddCommGroup E
inst✝³ : NormedSpace ℝ E
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace ℝ F
m : MeasurableSpace α
μ : Measure α
inst✝ : CompleteSpace F
T : Set α → E →L[ℝ] F
C : ℝ
hT : DominatedFinMeasAdditive μ T C
fs : ℕ → α → E
f : α → E
bound : α → ℝ
fs_measurable : ∀ (n : ℕ), AEStronglyMeasurable (fs n) μ
bound_integrable : Integrable bound μ
h_bound : ∀ (n : ℕ), ∀ᵐ (a : α) ∂μ, ‖fs n a‖ ≤ bound a
h_lim : ∀ᵐ (a : α) ∂μ, Tendsto (fun n => fs n a) atTop (𝓝 (f a))
f_measurable : AEStronglyMeasurable f μ
fs_int : ∀ (n : ℕ), Integrable (fs n) μ
f_int : Integrable f μ
lintegral_norm_tendsto_zero : Tendsto (fun n => (∫⁻ (a : α), ENNReal.ofReal ‖fs n a - f a‖ ∂μ).toReal) atTop (𝓝 0)
⊢ Tendsto (fun e => ‖Integrable.toL1 (fs e) ⋯ - Integrable.toL1 f f_int‖) atTop (𝓝 0)

Proof state:
α : Type u_1
E : Type u_2
F : Type u_3
inst✝⁴ : NormedAddCommGroup E
inst✝³ : NormedSpace ℝ E
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace ℝ F
m : MeasurableSpace α
μ : Measure α
inst✝ : CompleteSpace F
T : Set α → E →L[ℝ] F
C : ℝ
hT : DominatedFinMeasAdditive μ T C
fs : ℕ → α → E
f : α → E
bound : α → ℝ
fs_measurable : ∀ (n : ℕ), AEStronglyMeasurable (fs n) μ
bound_integrable : Integrable bound μ
h_bound : ∀ (n : ℕ), ∀ᵐ (a : α) ∂μ, ‖fs n a‖ ≤ bound a
h_lim : ∀ᵐ (a : α) ∂μ, Tendsto (fun n => fs n a) atTop (𝓝 (f a))
f_measurable : AEStronglyMeasurable f μ
fs_int : ∀ (n : ℕ), Integrable (fs n) μ
f_int : Integrable f μ
lintegral_norm_tendsto_zero : Tendsto (fun n => (∫⁻ (a : α), ENNReal.ofReal ‖fs n a - f a‖ ∂μ).toReal) atTop (𝓝 0)
⊢ Tendsto (fun e => ‖Integrable.toL1 (fs e) ⋯ - Integrable.toL1 f f_int‖) atTop (𝓝 0)

Tactic:
convert lintegral_norm_tendsto_zero with n

Result:
case h.e'_3.h
α : Type u_1
E : Type u_2
F : Type u_3
inst✝⁴ : NormedAddCommGroup E
inst✝³ : NormedSpace ℝ E
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace ℝ F
m : MeasurableSpace α
μ : Measure α
inst✝ : CompleteSpace F
T : Set α → E →L[ℝ] F
C : ℝ
hT : DominatedFinMeasAdditive μ T C
fs : ℕ → α → E
f : α → E
bound : α → ℝ
fs_measurable : ∀ (n : ℕ), AEStronglyMeasurable (fs n) μ
bound_integrable : Integrable bound μ
h_bound : ∀ (n : ℕ), ∀ᵐ (a : α) ∂μ, ‖fs n a‖ ≤ bound a
h_lim : ∀ᵐ (a : α) ∂μ, Tendsto (fun n => fs n a) atTop (𝓝 (f a))
f_measurable : AEStronglyMeasurable f μ
fs_int : ∀ (n : ℕ), Integrable (fs n) μ
f_int : Integrable f μ
lintegral_norm_tendsto_zero : Tendsto (fun n => (∫⁻ (a : α), ENNReal.ofReal ‖fs n a - f a‖ ∂μ).toReal) atTop (𝓝 0)
n : ℕ
⊢ ‖Integrable.toL1 (fs n) ⋯ - Integrable.toL1 f f_int‖ = (∫⁻ (a : α), ENNReal.ofReal ‖fs n a - f a‖ ∂μ).toReal