Consider the class dictionary SELF-DESCRIBING
and the following method called 

Cd_graph {
  void display() bypassing -> *,tail,* to * (DisplayVisitor);
  {{
  void test(){
    TraversalGraph tg = new TraversalGraph(
      "from Cd_graph bypassing -> *,rest,* to Adj", Main.cg);
    System.out.println(tg);
    tg. traverse(this, new Visitor() {
	void before(Adj host){ System.out.println(host); }
    });
  }
  }}
}

called on the object corresponding to the sentence:

// class dictionary
Cd_graph = <first> Adj <rest> Adj_list.
Adj = <vertex> Vertex <ns> Neighbors ".".
Neighbors: Construct | Alternat.
Construct = "=" <c_ns> Any_vertex_list.
Alternat = ":" <first> Vertex "|" <second> Vertex.
Any_vertex : Labeled_vertex | Syntax_vertex.
Syntax_vertex = <string> String.
Labeled_vertex = "<" <label_name> Ident ">" 
                     <class_name> Vertex.
Adj_list: Cd_graph | Empty_cd_graph .
Any_vertex_list: Nany_vertex_list | Empty.
Nany_vertex_list = 
  <first> Any_vertex <rest> Any_vertex_list.
Empty = .
Empty_cd_graph = .
Vertex = <name> Ident.

///////////////
CountingVisitor = <total> int.
///////////////

Main = .

The output produced by test is:

Start set: [Cd_graph: {0}]
Copy 0:
 Nodes:
 Cd_graph
 Adj
 java.lang.Object
 java.io.Serializable
 Adj_list
 Edges:
 -> Cd_graph,first,Adj
 Edges to other copies:
Finish set: [Adj: {0}]
Adj@910040
 done 

Find the UNKNOWNs.