theorem extracted_formal_statement_281.{u_1, w, u} {Ω : Type u} [inst : MeasurableSpace Ω] {Z : Type w} {n : ℕ}
  {ι : Type u_1} {f : ι → Z → ℝ} {μ : Measure Ω} [inst_1 : IsProbabilityMeasure μ] [inst_2 : Nonempty ι]
  [inst_3 : Countable ι] {X : Ω → Z} (hf : ∀ (i : ι), Measurable (f i ∘ X)) {b : ℝ}
  (hf' : ∀ (i : ι) (z : Z), |f i z| ≤ b) (ω : (Fin n → Ω) × (Fin n → Ω)) (σ : Signs n) (a : σ ∈ Finset.univ) :
  BddAbove (Set.range fun i => ∑ k, |↑↑(σ k) * f i (X (ω.1 k))|) := sorry

State before:
case h.B
Ω : Type u
inst✝³ : MeasurableSpace Ω
Z : Type w
n : ℕ
ι : Type u_1
f : ι → Z → ℝ
μ : Measure Ω
inst✝² : IsProbabilityMeasure μ
inst✝¹ : Nonempty ι
inst✝ : Countable ι
X : Ω → Z
hf : ∀ (i : ι), Measurable (f i ∘ X)
b : ℝ
hf' : ∀ (i : ι) (z : Z), |f i z| ≤ b
ω : (Fin n → Ω) × (Fin n → Ω)
σ : Signs n
a✝ : σ ∈ Finset.univ
⊢ BddAbove (Set.range fun i => ∑ k, |↑↑(σ k) * f i (X (ω.1 k))|)

Tactic: apply bdd_above_aux hf'

State after:

Relevant lemmas:
bdd_above_aux : ∀ {Ω : Type u} {Z : Type w} {n : ℕ} {ι : Type u_1} {f : ι → Z → ℝ} {X : Ω → Z} {b : ℝ},
  (∀ (i : ι) (z : Z), |f i z| ≤ b) →
    ∀ (σ : Signs n) (ω : Fin n → Ω), BddAbove (Set.range fun i => ∑ k, |↑↑(σ k) * f i (X (ω k))|)