def extension
      @extension ||= begin
        list = @xml.find('/e:epp/e:response/e:extension/node()').reject { |n| n.empty? }
        list.size > 1 ? list : list[0]
      end
    end
def extension
      @extension ||= begin
        list = @xml.find('/e:epp/e:response/e:extension/node()').reject { |n| n.empty? }
        list.size > 1 ? list : list[0]
      end
    end
Response extension block
 @return [XML::Node, Array<XML::Node>] extension