val mem : 'a key -> t -> bool
val add : 'a key -> 'a -> t -> t
val add_if_some : 'a key -> 'a option -> t -> t
val tag : unit key -> t -> t
val rem : 'a key -> t -> t
val find : 'a key -> t -> 'a option
val find_binding_by_name : string -> t -> binding option
val get : 'a key -> t -> 'a
val get_binding_by_name : string -> t -> binding
val fold : (binding -> 'a -> 'a) -> t -> 'a -> 'a
val authors : string list key
val description : string key
val homepage : string key
val licenses : string list key
val maintainers : string list key
val online_doc : string key
val synopsis : string key
val exe_name : string key