You can search for identifiers within the package.
in-package search v0.2.0
module IO : sig ... end
module Uid : sig ... end
type t = Device.t
type uid = Device.uid
type fd
type error
val pp_error : error Fmt.t
val create : t -> uid -> (fd, error) Stdlib.result IO.t
val append : t -> fd -> string -> unit IO.t
val close : t -> fd -> (unit, error) Stdlib.result IO.t