Immutable map
val mem : _ Key.t ‑> t ‑> bool
val find : 'a Key.t ‑> t ‑> 'a option
val find_exn : 'a Key.t ‑> t ‑> 'a
- Raises Not_found: if the key is not in the table.
val iter : (pair ‑> unit) ‑> t ‑> unit
val add_list : t ‑> pair list ‑> t
val of_list : pair list ‑> t
val to_list : t ‑> pair list