-- Mathlib/Probability/Independence/Kernel.lean
theorem iIndepSet.indep_generateFrom_of_disjoint {s : ι → Set Ω}
    (hsm : ∀ n, MeasurableSet (s n)) (hs : iIndepSet s κ μ) (S T : Set ι) (hST : Disjoint S T) :
    Indep (generateFrom { t | ∃ n ∈ S, s n = t }) (generateFrom { t | ∃ k ∈ T, s k = t }) κ μ

Proof state:
case inr.intro.intro.refine_4
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ IsPiSystem (piiUnionInter (fun k => {s k}) T)

Tactic:
exact isPiSystem_piiUnionInter _ (fun k => IsPiSystem.singleton _) _

Result:
no goals

Proof state:
case inl
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
S T : Set ι
hST : Disjoint S T
hs : iIndepSet s κ 0
⊢ Indep (generateFrom {t | ∃ n ∈ S, s n = t}) (generateFrom {t | ∃ k ∈ T, s k = t}) κ 0

Tactic:
simp

Result:
no goals

Proof state:
case inr.intro.intro.refine_3
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ IsPiSystem (piiUnionInter (fun k => {s k}) S)

Tactic:
exact isPiSystem_piiUnionInter _ (fun k => IsPiSystem.singleton _) _

Result:
no goals

Proof state:
case inr.intro.intro.refine_2
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
t : Set Ω
ht : t ∈ piiUnionInter (fun k => {s k}) T
⊢ ∀ (n : ι), generateFrom {s n} ≤ _mΩ

Tactic:
exact fun k => generateFrom_le fun t ht => (Set.mem_singleton_iff.1 ht).symm ▸ hsm k

Result:
no goals

Proof state:
case inr.intro.intro.refine_1
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
t : Set Ω
ht : t ∈ piiUnionInter (fun k => {s k}) S
⊢ ∀ (n : ι), generateFrom {s n} ≤ _mΩ

Tactic:
exact fun k => generateFrom_le fun t ht => (Set.mem_singleton_iff.1 ht).symm ▸ hsm k

Result:
no goals

Proof state:
case inr.intro.intro
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ Indep (generateFrom {t | ∃ n ∈ S, s n = t}) (generateFrom {t | ∃ k ∈ T, s k = t}) κ μ

Tactic:
apply Indep.congr (Filter.EventuallyEq.symm η_eq)

Result:
case inr.intro.intro
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ Indep (generateFrom {t | ∃ n ∈ S, s n = t}) (generateFrom {t | ∃ k ∈ T, s k = t}) η μ

Proof state:
case inr.intro.intro.refine_5
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ IndepSets (piiUnionInter (fun k => {s k}) S) (piiUnionInter (fun k => {s k}) T) η μ

Tactic:
exact indepSets_piiUnionInter_of_disjoint (iIndep.iIndepSets (fun n => rfl) (hs.congr η_eq)) hST

Result:
no goals

Proof state:
case inr.intro.intro
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ Indep (generateFrom (piiUnionInter (fun k => {s k}) S)) (generateFrom (piiUnionInter (fun k => {s k}) T)) η μ

Tactic:
refine
  IndepSets.indep'
    (fun t ht => generateFrom_piiUnionInter_le _ ?_ _ _ (measurableSet_generateFrom ht))
    (fun t ht => generateFrom_piiUnionInter_le _ ?_ _ _ (measurableSet_generateFrom ht)) ?_ ?_ ?_

Result:
case inr.intro.intro.refine_1
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
t : Set Ω
ht : t ∈ piiUnionInter (fun k => {s k}) S
⊢ ∀ (n : ι), generateFrom {s n} ≤ _mΩ

case inr.intro.intro.refine_2
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
t : Set Ω
ht : t ∈ piiUnionInter (fun k => {s k}) T
⊢ ∀ (n : ι), generateFrom {s n} ≤ _mΩ

case inr.intro.intro.refine_3
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ IsPiSystem (piiUnionInter (fun k => {s k}) S)

case inr.intro.intro.refine_4
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ IsPiSystem (piiUnionInter (fun k => {s k}) T)

case inr.intro.intro.refine_5
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ IndepSets (piiUnionInter (fun k => {s k}) S) (piiUnionInter (fun k => {s k}) T) η μ

Proof state:
case inr.intro.intro
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ Indep (generateFrom {t | ∃ n ∈ S, s n = t}) (generateFrom {t | ∃ k ∈ T, s k = t}) η μ

Tactic:
rw [← generateFrom_piiUnionInter_singleton_left, ← generateFrom_piiUnionInter_singleton_left]

Result:
case inr.intro.intro
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
s : ι → Set Ω
hsm : ∀ (n : ι), MeasurableSet (s n)
hs : iIndepSet s κ μ
S T : Set ι
hST : Disjoint S T
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
⊢ Indep (generateFrom (piiUnionInter (fun k => {s k}) S)) (generateFrom (piiUnionInter (fun k => {s k}) T)) η μ