def rest_rexml
      ea = REXML::Element.new self.class::RSRC_OBJECT_KEY.to_s
      ea.add_element('name').text = @name
      ea.add_element('description').text = @description
      ea.add_element('data_type').text = @data_type
      ea.add_element('inventory_display').text = @web_display

      it = ea.add_element('input_type')
      it.add_element('type').text = @input_type
      if @input_type == 'Pop-up Menu'
        pcs = it.add_element('popup_choices')
        @popup_choices.each { |pc| pcs.add_element('choice').text = pc }
      end
      ea
    end
def rest_rexml
      ea = REXML::Element.new self.class::RSRC_OBJECT_KEY.to_s
      ea.add_element('name').text = @name
      ea.add_element('description').text = @description
      ea.add_element('data_type').text = @data_type
      ea.add_element('inventory_display').text = @web_display

      it = ea.add_element('input_type')
      it.add_element('type').text = @input_type
      if @input_type == 'Pop-up Menu'
        pcs = it.add_element('popup_choices')
        @popup_choices.each { |pc| pcs.add_element('choice').text = pc }
      end
      ea
    end
Return a REXML object for this ext attr, with the current values.
 Subclasses should augment this in their rest_xml methods
 then return it .to_s, for saving or updating