# File lib/merb-assets/assets_mixin.rb, line 400
    def include_required_css(options = {})
      return '' if @required_css.nil? || @required_css.empty?
      @required_css.map do |req_css|
        if req_css.last.is_a?(Hash)
          css_include_tag(*(req_css[0..-2] + [options.merge(req_css.last)]))
        else
          css_include_tag(*(req_css + [options]))
        end
      end.join
    end