val is_subset : comparator:('a, 'cmp) Comparator.t ‑> ('a, 'cmp) named ‑> of_:('a, 'cmp) named ‑> unit Or_error.t
val equal : comparator:('a, 'cmp) Comparator.t ‑> ('a, 'cmp) named ‑> ('a, 'cmp) named ‑> unit Or_error.t