def data=(data)
      raise "not yet used"
      raise "Data nil or invalid" if data.nil? or data.size == 0
      delete_all
      @data = data
      tme = TreeModelEvent.new(0, @data.length-1,:ALL_COLUMNS,  self, :INSERT)
      fire_handler :TREE_MODEL_EVENT, tme
    end
def data=(data)
      raise "not yet used"
      raise "Data nil or invalid" if data.nil? or data.size == 0
      delete_all
      @data = data
      tme = TreeModelEvent.new(0, @data.length-1,:ALL_COLUMNS,  self, :INSERT)
      fire_handler :TREE_MODEL_EVENT, tme
    end
for those quick cases when you wish to replace all the data
 and not have an event per row being generated