∀ {α : Type u_1} {instOrd : Ord α} {β : Type u_2} {t₁ t₂ : Std.DTreeMap.Internal.Impl α fun x => β} [Std.TransOrd α],
  t₁.WF →
    t₂.WF → t₁.Equiv t₂ → ∀ {k : α} {he : ∃ a ∈ t₁, compare a k = Ordering.lt}, ∃ a ∈ t₂, compare a k = Ordering.lt