/**
  * Returns a new request for the given connection and operation.
  *
  * @param string $operation An operation from Operations.
  * @param array  $data      [optional] Extra data to send.
  */
 public function __construct($operation, $data = null)
 {
     $this->connection = AmazonSDK::getDefaultConnection();
     $this->operation = $operation;
     $this->data = $data;
 }