# File lib/xml/dom2/nodelist.rb, line 183
      def +(nodes)
        if nodes.nil?
          NodeList.new(@nodes)
        elsif nodes.is_a?(Array)
          NodeList.new(@nodes + nodes)
        elsif nodes.is_a?(NodeList)
          NodeList.new(@nodes + nodes.to_a)
        elsif nodes.is_a?(Node)
          NodeList.new(@nodes + [nodes])
        else
          raise "parameter error"
        end
      end