- type t
- Type of stores 
- type 'a field
- Type of field of such stores 
- val field : unit -> 'a field
- Create a new field 
- val empty : t
- Empty store 
- val set : t -> 'a field -> 'a -> t
- Set a field 
- val get : t -> 'a field -> 'a option
- Get the value of a field, if any 
- val remove : t -> 'a field -> t
- Unset the value of the field 
- val merge : t -> t -> t
- merge s1 s2adds all the fields of- s1into- s2.