# File rss/trackback.rb, line 242
        def required_prefix
          TRACKBACK_PREFIX
        end

# File rss/trackback.rb, line 246
        def required_uri
          TRACKBACK_URI
        end

# File rss/trackback.rb, line 252
      def to_s(convert=true, indent=calc_indent)
        if @content
          rv = %Q[#{indent}<#{TRACKBACK_PREFIX}:ping>]
          rv << h(@content)
          rv << %Q[</#{TRACKBACK_PREFIX}:ping>]
          rv = @converter.convert(rv) if convert and @converter
          rv
        else
          ''
        end
      end