val load_api_versions : string -> unit
(** Load the data from the named file. *)
-val lookup_api_version : string -> string
+val lookup_api_version : string -> string option
(** [lookup_api_version c_api] looks up the version that the C API call
(which must be the full C name, eg. ["guestfs_launch"]) was
- added. This returns the version string, eg. ["0.3"]. *)
+ added. This returns the version string, eg. [Some "0.3"], or
+ [None] if no version could be found. *)