`sig
type t
val get_structure : DGraphTreeModel.S.TreeManipulation.t -> Tree.t
val get_tree_vertices :
Tree.V.label -> DGraphTreeModel.S.TreeManipulation.t -> Tree.V.t list
val get_graph_vertex :
Tree.V.t -> DGraphTreeModel.S.TreeManipulation.t -> Tree.V.label
val is_ghost_node :
Tree.V.t -> DGraphTreeModel.S.TreeManipulation.t -> bool
val is_ghost_edge :
Tree.E.t -> DGraphTreeModel.S.TreeManipulation.t -> bool
end`