obtain ⟨e, he₀, he₁⟩ := this
case intro
α : Type u_1
β : Type u_2
γ : Type u_3
G G₁ G₂ G₃ : SimpleGraph α
H : SimpleGraph β
I : SimpleGraph γ
hG : G ≠ ⊥
H' : (H \ fromEdgeSet (⋃ H', ⋃ (hH' : Nonempty (G ≃g H'.coe)), {⋯.some})).Subgraph
hGH' : Nonempty (G ≃g H'.coe)
hH' : (Subgraph.map (Hom.ofLE ⋯) H').edgeSet.Nonempty
this : hH'.some ∈ Sym2.map Subtype.val '' (Subgraph.map (Hom.ofLE ⋯) H').coe.edgeSet
⊢ False
case intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
G G₁ G₂ G₃ : SimpleGraph α
H : SimpleGraph β
I : SimpleGraph γ
hG : G ≠ ⊥
H' : (H \ fromEdgeSet (⋃ H', ⋃ (hH' : Nonempty (G ≃g H'.coe)), {⋯.some})).Subgraph
hGH' : Nonempty (G ≃g H'.coe)
hH' : (Subgraph.map (Hom.ofLE ⋯) H').edgeSet.Nonempty
e : Sym2 ↑(Subgraph.map (Hom.ofLE ⋯) H').verts
he₀ : e ∈ (Subgraph.map (Hom.ofLE ⋯) H').coe.edgeSet
he₁ : Sym2.map Subtype.val e = hH'.some
⊢ False