∀ {α : Type u} {β : α → Type v} {cmp : α → α → Ordering} {t : Std.DTreeMap α β cmp} [Std.TransCmp cmp] {k : α},
  (∀ (k' : α), t.minKey? = some k' → (cmp k k').isLE = true) ↔ ∀ k' ∈ t, (cmp k k').isLE = true