You can search for identifiers within the package.
in-package search v0.2.0
type !'a0 info = string * ('a -> Sexplib.Sexp.t)
val create : 'a info -> 'a key
val info : 'a key -> 'a info
type t
val hide_type : 'a key -> t
val equal : t -> t -> bool
val compare : t -> t -> int