Mark.marked_map
constraint 'self = < visit_marked : 'a. ( 'env -> 'a -> 'a ) -> 'env -> ( 'a, 'm ) ed -> ( 'a, 'm ) ed.. >
method visit_marked : 'a. ( 'env -> 'a -> 'a ) -> 'env -> ( 'a, 'm ) ed -> ( 'a, 'm ) ed