You can search for identifiers within the package.
in-package search v0.2.0
type 'a t = (module KEY_IMPL with type t = 'a)
val _n : int ref
val create : unit -> (module KEY_IMPL with type t = 'k)
val id : (module KEY_IMPL with type t = 'k) -> int
val equal : 'a 'b. 'a t -> 'b t -> bool