# File rss/trackback.rb, line 74
      def initialize(resource=nil)
        super()
        @resource = resource
      end

# File rss/trackback.rb, line 58
        def required_prefix
          TRACKBACK_PREFIX
        end

# File rss/trackback.rb, line 62
        def required_uri
          TRACKBACK_URI
        end

# File rss/trackback.rb, line 79
      def to_s(convert=true, indent=calc_indent)
        if @resource
          rv = %Q[#{indent}<#{TRACKBACK_PREFIX}:ping ]
          rv << %Q[#{::RSS::RDF::PREFIX}:resource="#{h @resource}"/>]
          rv = @converter.convert(rv) if convert and @converter
          rv
        else
          ''
        end
      end