∀ {α : Type u} {β : α → Type v} {cmp : α → α → Ordering} {m₁ m₂ : Std.DTreeMap α β cmp} [inst : (k : α) → BEq (β k)]
  [inst_1 : Std.LawfulEqCmp cmp] [Std.TransCmp cmp] [∀ (k : α), ReflBEq (β k)], m₁.Equiv m₂ → (m₁ == m₂) = true