`object
method abort : unit -> unit
method can_output : bool
method close_out : unit -> unit
method event_system : Unixqueue.event_system
method flush : unit -> unit
method output : Bytes.t -> int -> int -> int
method pos_out : int
method request_notification : (unit -> bool) -> unit
method request_proxy_notification :
(unit Uq_engines.engine -> bool) -> unit
method state : unit Uq_engines.engine_state
end`