`sig
class type ['t] job_handler_engine_type =
object
method abort : unit -> unit
method event_system : Unixqueue.event_system
method job : Shell_sys.job
method job_instance : Shell_sys.job_instance
method request_notification : (unit -> bool) -> unit
method state : 't Uq_engines.engine_state
end
class call_engine :
?ignore_error_code:bool ->
?mode:Shell_sys.group_mode ->
?stdin:Shell.producer ->
?stdout:Shell.consumer ->
?stderr:Shell.consumer ->
Shell_sys.command list ->
Unixqueue.event_system -> [Shell_sys.job_status] job_handler_engine_type
end`