Map.Symmetric_diff_element
include Sexpable.S2 with type ('k, 'v) t := ('k, 'v) t
val t_of_sexp : (Sexplib0.Sexp.t -> 'a) -> (Sexplib0.Sexp.t -> 'b) -> Sexplib0.Sexp.t -> ('a, 'b) t
val sexp_of_t : ('a -> Sexplib0.Sexp.t) -> ('b -> Sexplib0.Sexp.t) -> ('a, 'b) t -> Sexplib0.Sexp.t