You can search for identifiers within the package.
in-package search v0.2.0
type 'a subst
val empty_subst : unit -> 'a subst
val add_to_subst : 'a subst -> string -> ('a -> string) -> unit
val add_to_copy : 'a subst -> string -> ('a -> string) -> 'a subst
val subst_of_list : (string * ('a -> string)) list -> 'a subst
val subst : 'a subst -> string -> 'a -> int * string
val iter_subst : 'a subst -> string -> 'a -> int * string