OCaml library : Effect.Shallow

`sig
type ('a, 'b) continuation
val fiber : ('a -> 'b) -> ('a, 'b) Effect.Shallow.continuation
type ('a, 'b) handler = {
retc : 'a -> 'b;
exnc : exn -> 'b;
effc :
'c. 'c Effect.t -> (('c, 'a) Effect.Shallow.continuation -> 'b) option;
}
val continue_with :
('c, 'a) Effect.Shallow.continuation ->
'c -> ('a, 'b) Effect.Shallow.handler -> 'b
val discontinue_with :
('c, 'a) Effect.Shallow.continuation ->
exn -> ('a, 'b) Effect.Shallow.handler -> 'b
val discontinue_with_backtrace :
('a, 'b) Effect.Shallow.continuation ->
exn ->
Stdlib.Printexc.raw_backtrace -> ('b, 'c) Effect.Shallow.handler -> 'c
external get_callstack :
('a, 'b) Effect.Shallow.continuation ->
int -> Stdlib.Printexc.raw_backtrace = "caml_get_continuation_callstack"
end`