type path = Key.t listtype 'a node = 'a Trie.Make(Key).node
val create : 'a option -> 'a nodeval get : 'a node -> path -> 'a optionval set : 'a node -> path -> 'a -> unitval unset : 'a node -> path -> unitval sub : 'a node -> path -> 'a node optionval is_leaf : 'a node -> bool