# File lib/xml/dom/core.rb, line 1402
      def <<(nodes)
        if nodes.nil?
          ## no change
        elsif nodes.is_a?(Array)
          @nodes.concat(nodes)
        elsif nodes.is_a?(NodeList)
          @nodes.concat(nodes.to_a)
        elsif nodes.is_a?(Node)
          @nodes << nodes
        else
          raise "parameter error"
        end
        self
      end