# File gtk/sample/gtk-demo/tree_store.rb, line 173
    def create_model
      # create tree store
      model = Gtk::TreeStore.new(String,
                                 TrueClass,
                                 TrueClass,
                                 TrueClass,
                                 TrueClass,
                                 TrueClass,
                                 TrueClass,
                                 TrueClass)

      # add data to the tree store
      TOPLEVEL.each do |month_name, holidays|
        iter = model.append(nil)

        iter[HOLIDAY_NAME_COLUMN] = month_name
        (ALEX_COLUMN..DAVE_COLUMN).each do |index|
          iter[index] = false
        end

        # add children
        holidays.each do |holiday|
          child_iter = model.append(iter)
          child_iter[HOLIDAY_NAME_COLUMN] = holiday.label[0]
          %w(alex havoc tim owen dave).each_with_index do |person, i|
            child_iter[ALEX_COLUMN + i] = holiday[person]
          end
          child_iter[VISIBLE_COLUMN] = true
          child_iter[WORLD_COLUMN] = holiday.world_holiday
        end

      end

      return model
    end