You can search for identifiers within the package.
in-package search v0.2.0
type ('error, 'value) t =
| Error of 'error
| Value of 'value
val error : 'error -> ('error, 'value) t
val value : 'value -> ('error, 'value) t
val map : ('a -> 'b) -> ('error, 'a) t -> ('error, 'b) t