class [['a, 'b]] map_engine : map_done:('a -> 'b engine_state) -> ?map_error:exn -> 'b engine_state -> ?map_aborted:unit -> 'b engine_state -> ?propagate_working:bool -> 'a #engine -> ['b] engine
[['a, 'b]]
map_done:('a -> 'b engine_state) -> ?map_error:exn -> 'b engine_state -> ?map_aborted:unit -> 'b engine_state -> ?propagate_working:bool -> 'a #engine ->
['b]
engine