# File lib/css_parser/parser.rb, line 257
    def to_s(which_media = :all)
      out = String.new
      styles_by_media_types = {}
      each_selector(which_media) do |selectors, declarations, specificity, media_types|
        media_types.each do |media_type|
          styles_by_media_types[media_type] ||= []
          styles_by_media_types[media_type] << [selectors, declarations]
        end
      end

      styles_by_media_types.each_pair do |media_type, media_styles|
        media_block = (media_type != :all)
        out << "@media #{media_type} {\n" if media_block

        media_styles.each do |media_style|
          if media_block
            out << "  #{media_style[0]} {\n    #{media_style[1]}\n  }\n"
          else
            out << "#{media_style[0]} {\n#{media_style[1]}\n}\n"
          end
        end

        out << "}\n" if media_block
      end

      out
    end