You can search for identifiers within the package.
in-package search v0.2.0
type 'a t = private
| Zero
| Item of 'a
| Plus of 'a t * 'a t
val zero : 'a t
val of_item : 'a -> 'a t
val of_list : 'a list -> 'a t
val flatten : 'a t list -> 'a t
val plus : 'a t -> 'a t -> 'a t
val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b t -> 'a
val fold_right : ('a -> 'b -> 'b) -> 'a t -> 'b -> 'b
val hd : 'a t -> 'a
class 'a free_monoid : object ... end