code: func (e *SimpleEventHandler) Tree() *Graph {
  
  	g := make([]*Graph, e.max+2)
  	g[0] = New("_")
  	/*
  		println("ev.Tree", len(e.items), len(e.levels), e.max)
  
  		for i := 0; i < len(e.items); i++ {
  			fmt.Printf(" - %d %v\n", e.levels[i], e.items[i])
  		}
  	*/
  	for i := 0; i < len(e.items); i++ {
  		lv := e.levels[i] + 1
  		item := e.items[i]
  
  		n := New(item)
  		g[lv] = n
  		g[lv-1].Add(n)
  	}
  
  	return g[0]
  }
docs: // Tree returns the Graph object built from
  // the events sent to this event handler.
  //