# File lib/org-ruby/html_output_buffer.rb, line 192
    def add_line_attributes headline
      if @options[:export_heading_number] then
        level = headline.level
        heading_number = get_next_headline_number(level)
        @output << "<span class=\"heading-number heading-number-#{level}\">#{heading_number}</span> "
      end
      if @options[:export_todo] and headline.keyword then
        keyword = headline.keyword
        @output << "<span class=\"todo-keyword #{keyword}\">#{keyword}</span> "
      end
    end