# File lib/aws/dynamo_db/batch_get.rb, line 175
      def convert_unprocessed_keys response

        return nil if response.data['UnprocessedKeys'].empty?

        # convert the json response keys into symbolized keys
        str2sym = lambda do |key_desc|
          type, value = key_desc.to_a.flatten
          case type
          when "S" then { :s => value }
          when "N" then { :n => value }
          else
            raise "unhandled key type: #{type}"
          end
        end

        request_items = {}
        response.data['UnprocessedKeys'].each_pair do |table,keys|

          request_items[table] = {}

          request_items[table][:attributes_to_get] = keys['AttributesToGet'] if
            keys['AttributesToGet']

          request_items[table][:keys] = keys['Keys'].collect do |desc|
            key = {}
            key[:hash_key_element] = str2sym.call(desc['HashKeyElement'])
            key[:range_key_element] = str2sym.call(desc['RangeKeyElement']) if
              desc['RangeKeyElement']
            key
          end

        end
        request_items

      end