-- Lean 4 proof step from Mathlib.Topology.Category.Stonean.EffectiveEpi (hypothesis)
Goal:
B X : Stonean
π : X ⟶ B
tfae_1_to_2 : ∀ (a : EffectiveEpi π), Epi π
tfae_2_iff_3 :
  Epi π ↔
    Function.Surjective (α :=
      (fun (X : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
          (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u))
        X)
      (β :=
      (fun (X : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
          (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u))
        B)
      (⇑(ConcreteCategory.hom (FC :=
            fun (x1 x2 : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
            C((↑(x1.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u),
              (↑(x2.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u)))
            (CC := fun (X : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
            (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u)) π) :
        (a : (fun (X : CompHausLike fun (X : TopCat) ↦ ExtremallyDisconnected (↑X : Type u)) ↦ (↑X.toTop : Type u)) X) →
          (fun (X : CompHausLike fun (X : TopCat) ↦ ExtremallyDisconnected (↑X : Type u)) ↦ (↑X.toTop : Type u)) B)
⊢ [EffectiveEpi π, Epi π,
      Function.Surjective (α :=
        (fun (X : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
            (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u))
          X)
        (β :=
        (fun (X : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
            (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u))
          B)
        (⇑(ConcreteCategory.hom (FC :=
              fun (x1 x2 : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
              C((↑(x1.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u),
                (↑(x2.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u)))
              (CC := fun (X : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
              (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u)) π) :
          (a :
              (fun (X : CompHausLike fun (X : TopCat) ↦ ExtremallyDisconnected (↑X : Type u)) ↦ (↑X.toTop : Type u))
                X) →
            (fun (X : CompHausLike fun (X : TopCat) ↦ ExtremallyDisconnected (↑X : Type u)) ↦ (↑X.toTop : Type u))
              B)].TFAE
have tfae_3_to_1 : ∀
  (a :
    Function.Surjective (α :=
      (fun (X : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
          (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u))
        X)
      (β :=
      (fun (X : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
          (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u))
        B)
      (⇑(ConcreteCategory.hom (FC :=
            fun (x1 x2 : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
            C((↑(x1.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u),
              (↑(x2.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u)))
            (CC := fun (X : CompHausLike fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u)) ↦
            (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ ExtremallyDisconnected.{u} (↑X : Type u))) : Type u)) π) :
        (a : (fun (X : CompHausLike fun (X : TopCat) ↦ ExtremallyDisconnected (↑X : Type u)) ↦ (↑X.toTop : Type u)) X) →
          (fun (X : CompHausLike fun (X : TopCat) ↦ ExtremallyDisconnected (↑X : Type u)) ↦ (↑X.toTop : Type u)) B)),
  EffectiveEpi π
Tactic: tfae_have 3 → 1 := fun hπ ↦ ⟨⟨effectiveEpiStruct π hπ⟩⟩