∀ {α : Type u_1} {β : Type u_2} {γ : Type u_3} [inst : DecidableEq α] [inst_1 : DecidableEq β] [inst_2 : DecidableEq γ]
  (x : α × β × γ), SimpleGraph.TripartiteFromTriangles.toTriangle x = {Sum3.in₀ x.1, Sum3.in₁ x.2.1, Sum3.in₂ x.2.2}