type 'a sequence
= ('a ‑> unit) ‑> unit
type 'a printer
= Format.formatter ‑> 'a ‑> unit
module type OrderedType = Set.OrderedType
module type S : sig ... end
module Make : functor (O : Set.OrderedType) -> S with type Make.t = Set.Make(O).t and type Make.elt = O.t