∀ {α : Type u} {β : Type v} {cmp : α → α → Ordering} {t : Std.ExtTreeMap α β cmp} [inst : Std.TransCmp cmp]
  [inst_1 : BEq α] [Std.LawfulBEqCmp cmp] {l : List (α × β)} {k : α},
  (List.map Prod.fst l).contains k = false → (t.insertMany l)[k]? = t[k]?