module Key:sig..end
type 'a t 
create name to_sexp generates a fresh key.
      Note: If type 'a doesn't support sexp conversion, then a good
            practice is to use sexp_of_opaque as the converter.val create : string -> ('a -> Sexp.t) -> 'a tval sexp_of_t : ('a -> Sexplib.Sexp.t) -> 'a t -> Sexplib.Sexp.tcreate name to_sexp generates a fresh key.
      Note: If type 'a doesn't support sexp conversion, then a good
            practice is to use sexp_of_opaque as the converter.