∀ {α : Type u} {β : α → Type v} {cmp : α → α → Ordering} {t : Std.ExtDTreeMap α β cmp} [inst : Std.TransCmp cmp]
  [inst_1 : Std.LawfulEqCmp cmp] {k : α} {f : β k → β k} {he : t.modify k f ≠ ∅}, (t.modify k f).minKey he = t.minKey ⋯