    # File lib/chef/resource.rb, line 256
        def add_notification(action, resources, timing=:delayed)
          resources = [resources].flatten
          resources.each do |resource|
            case timing.to_s
            when 'delayed'
              notifies_delayed(action, resource)
            when 'immediate', 'immediately'
              notifies_immediately(action, resource)
            else
              raise ArgumentError,  "invalid timing: #{timing} for notifies(#{action}, #{resources.inspect}, #{timing}) resource #{self} "\
                                    "Valid timings are: :delayed, :immediate, :immediately"
            end
          end

          true
        end