private theorem lintegral_rpow_tsum_coe_nnnorm_sub_le_tsum {f : ℕ → α → E}
    (hf : ∀ n, AEStronglyMeasurable (f n) μ) {p : ℝ} (hp1 : 1 ≤ p) {B : ℕ → ℝ≥0∞}
    (h :
      ∀ n,
        (∫⁻ a, (∑ i in Finset.range (n + 1), ‖f (i + 1) a - f i a‖₊ : ℝ≥0∞) ^ p ∂μ) ≤
          (∑' i, B i) ^ p) :
    (∫⁻ a, (∑' i, ‖f (i + 1) a - f i a‖₊ : ℝ≥0∞) ^ p ∂μ) ^ (1 / p) ≤ ∑' i, B i := by
  have hp_pos : 0 < p := zero_lt_one.trans_le hp1
  suffices h_pow : (∫⁻ a, (∑' i, ‖f (i + 1) a - f i a‖₊ : ℝ≥0∞) ^ p ∂μ) ≤ (∑' i, B i) ^ p
  · rwa [← ENNReal.le_rpow_one_div_iff (by simp [hp_pos] : 0 < 1 / p), one_div_one_div]
  have h_tsum_1 :
    ∀ g : ℕ → ℝ≥0∞, ∑' i, g i = atTop.liminf fun n => ∑ i in Finset.range (n + 1), g i := by
    intro g
    rw [ENNReal.tsum_eq_liminf_sum_nat, ← liminf_nat_add _ 1]
  simp_rw [h_tsum_1 _]
  rw [← h_tsum_1]
  have h_liminf_pow :
    (∫⁻ a, (atTop.liminf
      fun n => ∑ i in Finset.range (n + 1), (‖f (i + 1) a - f i a‖₊ : ℝ≥0∞)) ^ p ∂μ) =
      ∫⁻ a, atTop.liminf
        fun n => (∑ i in Finset.range (n + 1), (‖f (i + 1) a - f i a‖₊ : ℝ≥0∞)) ^ p ∂μ := by
    refine' lintegral_congr fun x => _
    have h_rpow_mono := ENNReal.strictMono_rpow_of_pos (zero_lt_one.trans_le hp1)
    have h_rpow_surj := (ENNReal.rpow_left_bijective hp_pos.ne.symm).2
    refine' (h_rpow_mono.orderIsoOfSurjective _ h_rpow_surj).liminf_apply _ _ _ _
    

Proof state:
case refine'_1
α : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
m m0 : MeasurableSpace α
p✝ : ℝ≥0∞
q : ℝ
μ ν : Measure α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedAddCommGroup G
f : ℕ → α → E
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
p : ℝ
hp1 : 1 ≤ p
B : ℕ → ℝ≥0∞
h : ∀ (n : ℕ), ∫⁻ (a : α), (∑ i in Finset.range (n + 1), ↑‖f (i + 1) a - f i a‖₊) ^ p ∂μ ≤ (∑' (i : ℕ), B i) ^ p
hp_pos : 0 < p
h_tsum_1 : ∀ (g : ℕ → ℝ≥0∞), ∑' (i : ℕ), g i = liminf (fun n => ∑ i in Finset.range (n + 1), g i) atTop
x : α
h_rpow_mono : StrictMono fun x => x ^ p
h_rpow_surj : Function.Surjective fun y => y ^ p
⊢ IsBoundedUnder (fun x x_1 => x ≥ x_1) atTop fun n => ∑ i in Finset.range (n + 1), ↑‖f (i + 1) x - f i x‖₊
case refine'_2
α : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
m m0 : MeasurableSpace α
p✝ : ℝ≥0∞
q : ℝ
μ ν : Measure α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedAddCommGroup G
f : ℕ → α → E
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
p : ℝ
hp1 : 1 ≤ p
B : ℕ → ℝ≥0∞
h : ∀ (n : ℕ), ∫⁻ (a : α), (∑ i in Finset.range (n + 1), ↑‖f (i + 1) a - f i a‖₊) ^ p ∂μ ≤ (∑' (i : ℕ), B i) ^ p
hp_pos : 0 < p
h_tsum_1 : ∀ (g : ℕ → ℝ≥0∞), ∑' (i : ℕ), g i = liminf (fun n => ∑ i in Finset.range (n + 1), g i) atTop
x : α
h_rpow_mono : StrictMono fun x => x ^ p
h_rpow_surj : Function.Surjective fun y => y ^ p
⊢ IsCoboundedUnder (fun x x_1 => x ≥ x_1) atTop fun n => ∑ i in Finset.range (n + 1), ↑‖f (i + 1) x - f i x‖₊
case refine'_3
α : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
m m0 : MeasurableSpace α
p✝ : ℝ≥0∞
q : ℝ
μ ν : Measure α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedAddCommGroup G
f : ℕ → α → E
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
p : ℝ
hp1 : 1 ≤ p
B : ℕ → ℝ≥0∞
h : ∀ (n : ℕ), ∫⁻ (a : α), (∑ i in Finset.range (n + 1), ↑‖f (i + 1) a - f i a‖₊) ^ p ∂μ ≤ (∑' (i : ℕ), B i) ^ p
hp_pos : 0 < p
h_tsum_1 : ∀ (g : ℕ → ℝ≥0∞), ∑' (i : ℕ), g i = liminf (fun n => ∑ i in Finset.range (n + 1), g i) atTop
x : α
h_rpow_mono : StrictMono fun x => x ^ p
h_rpow_surj : Function.Surjective fun y => y ^ p
⊢ IsBoundedUnder (fun x x_1 => x ≥ x_1) atTop fun x_1 =>
    (StrictMono.orderIsoOfSurjective (fun x => x ^ p) h_rpow_mono h_rpow_surj)
      (∑ i in Finset.range (x_1 + 1), ↑‖f (i + 1) x - f i x‖₊)
case refine'_4
α : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
m m0 : MeasurableSpace α
p✝ : ℝ≥0∞
q : ℝ
μ ν : Measure α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedAddCommGroup G
f : ℕ → α → E
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
p : ℝ
hp1 : 1 ≤ p
B : ℕ → ℝ≥0∞
h : ∀ (n : ℕ), ∫⁻ (a : α), (∑ i in Finset.range (n + 1), ↑‖f (i + 1) a - f i a‖₊) ^ p ∂μ ≤ (∑' (i : ℕ), B i) ^ p
hp_pos : 0 < p
h_tsum_1 : ∀ (g : ℕ → ℝ≥0∞), ∑' (i : ℕ), g i = liminf (fun n => ∑ i in Finset.range (n + 1), g i) atTop
x : α
h_rpow_mono : StrictMono fun x => x ^ p
h_rpow_surj : Function.Surjective fun y => y ^ p
⊢ IsCoboundedUnder (fun x x_1 => x ≥ x_1) atTop fun x_1 =>
    (StrictMono.orderIsoOfSurjective (fun x => x ^ p) h_rpow_mono h_rpow_surj)
      (∑ i in Finset.range (x_1 + 1), ↑‖f (i + 1) x - f i x‖₊)

Next tactic:
all_goals isBoundedDefault