def delete_all
      raise "not yet used"
      len = @data.length-1
      @data=[]
      tme = TreeModelEvent.new(0, len,:ALL_COLUMNS,  self, :DELETE)
      fire_handler :TREE_MODEL_EVENT, tme
    end
def delete_all
      raise "not yet used"
      len = @data.length-1
      @data=[]
      tme = TreeModelEvent.new(0, len,:ALL_COLUMNS,  self, :DELETE)
      fire_handler :TREE_MODEL_EVENT, tme
    end
added 2009-01-17 21:36
 Use with caution, does not call events per row