∀ {α : Type u} {β : α → Type v} {instOrd : Ord α} [Std.TransOrd α] {l : List ((a : α) × β a)} {k k' : α},
  compare k k' = Ordering.eq →
    List.Pairwise (fun a b => ¬compare a.fst b.fst = Ordering.eq) l →
      k ∈ List.map Sigma.fst l → (↑(Std.DTreeMap.Internal.Impl.empty.insertMany l ⋯)).getKey? k' = some k