Read_write_pairSourceRead_write is like Dirpair, except "buy/sell" has been changed to "read/write".
val sexp_of_any :
('a -> Sexplib0.Sexp.t) ->
('z -> Sexplib0.Sexp.t) ->
('a, 'z) any ->
Sexplib0.Sexp.tval any_of_sexp :
(Sexplib0.Sexp.t -> 'a) ->
(Sexplib0.Sexp.t -> 'z) ->
Sexplib0.Sexp.t ->
('a, 'z) any