Returns [nil] if [n == nil].
*)
+val is_leaf : t -> node -> bool
+(** Return true if the node is a *)
+
val tag : t -> node -> QName.t
(** Returns the label of a given node *)
(** Returns the position of a node in pre-order in the tree. The
root has preorder 0. [nil] has pre-order [-1].
*)
+
+val print_xml_preorder : out_channel -> t -> node -> unit
+(** Outputs the tree with IDs for nodes as an XML document on the
+ given output_channel *)