CCGraph.Lazy_tree
type ('v, 'e) t = {
vertex : 'v;
children : ('e * ('v, 'e) t) list Stdlib.Lazy.t;
}
val map_v : ('a -> 'b) -> ('a, 'e) t -> ('b, 'e) t
val fold_v : ('acc -> 'v -> 'acc) -> 'acc -> ('v, _) t -> 'acc