# File lib/chef/resource.rb, line 34
      def duplicates?(other_notification)
        unless other_notification.respond_to?(:resource) && other_notification.respond_to?(:action)
          msg = "only duck-types of Chef::Resource::Notification can be checked for duplication "\
                "you gave #{other_notification.inspect}"
          raise ArgumentError, msg
        end
        other_notification.resource == resource && other_notification.action == action
      end