∀ {α : Type u} {β : Type v} {cmp : α → α → Ordering} {t : Std.TreeMap α β cmp} {m : Type w → Type w'} [inst : Monad m]
  [LawfulMonad m] {f : α → β → m PUnit.{w + 1}}, Std.TreeMap.forM f t = forM t fun a => f a.1 a.2