You can search for identifiers within the package.
in-package search v0.2.0
module X : Maker_concrete_key1
type ('h, _) key = 'h X.key
module Key (Hash : Hash.S) (Value : Type.S) : Key.S with type t = (Hash.t, Value.t) key and type hash = Hash.t
module Make (Hash : Hash.S) (Value : Type.S) : sig ... end