# File lib/nokogiri/xml/node_set.rb, line 108
      def attr key, value = nil, &blk
        if value or blk
          each do |el|
            el.set_attribute(key, value || blk[el])
          end
          return self      
        end    
        if key.is_a? Hash
          key.each { |k,v| self.attr(k,v) }
          return self
        else
          return self[0].get_attribute(key)
        end
      end