    # File lib/nokogiri/xml/node_set.rb, line 90
          def css *paths
            ns = paths.last.is_a?(Hash) ? paths.pop :
              (document.root ? document.root.namespaces : {})

            sub_set = NodeSet.new(document)

            xpaths = paths.map { |rule|
              [
                CSS.xpath_for(rule.to_s, :prefix => ".//", :ns => ns),
                CSS.xpath_for(rule.to_s, :prefix => "self::", :ns => ns)
              ].join(' | ')
            }
            each do |node|
              sub_set += node.xpath(*(xpaths + [ns]))
            end
            document.decorate(sub_set)
            sub_set
          end