def compress_css(paths, variant=nil, asset_url=nil)
      @asset_contents = {}
      css = concatenate_and_tag_assets(paths, variant)
      css = @css_compressor.compress(css) if Jammit.compress_assets
      case variant
      when nil      then return css
      when :datauri then return with_data_uris(css)
      when :mhtml   then return with_mhtml(css, asset_url)
      else raise PackageNotFound, "\"#{variant}\" is not a valid stylesheet variant"
      end
    end
def compress_css(paths, variant=nil, asset_url=nil)
      @asset_contents = {}
      css = concatenate_and_tag_assets(paths, variant)
      css = @css_compressor.compress(css) if Jammit.compress_assets
      case variant
      when nil      then return css
      when :datauri then return with_data_uris(css)
      when :mhtml   then return with_mhtml(css, asset_url)
      else raise PackageNotFound, "\"#{variant}\" is not a valid stylesheet variant"
      end
    end
Concatenate and compress a list of CSS stylesheets. When compressing a
 :datauri or :mhtml variant, post-processes the result to embed
 referenced assets.