    # File lib/compass/sass_extensions/functions/urls.rb, line 8
      def self.included(base)
        base.send(:include, StylesheetUrl) unless has?(base, :stylesheet_url)
        base.send(:include, FontUrl) unless has?(base, :font_url)
        base.send(:include, ImageUrl) unless has?(base, :image_url)
        base.send(:include, GeneratedImageUrl) unless has?(base, :generated_image_url)
      end