# File lib/aws/dynamo_db/batch_write.rb, line 237
      def str2sym key_desc
        type = key_desc.keys.first
        value = key_desc[type]
        case type
        when "S"  then { :s  => value }
        when "N"  then { :n  => value }
        when "SS" then { :ss => value }
        when "NS" then { :ns => value }
        else
          raise "unhandled key type: #{type.inspect}"
        end
      end