You can search for identifiers within the package.
in-package search v0.2.0
type ('b, 'a) t
val map : ('a, 'u) t -> f:('a -> 'b) -> ('b, 'u) t
val contra_map : ('u, 'b) t -> f:('a -> 'b) -> ('u, 'a) t
val both : ('a, 'i) t -> ('b, 'i) t -> ('a * 'b, 'i) t