protected function _normalizeIterable($iterable)
    {
        if (
                is_array($iterable) ||
                $iterable instanceof Traversable ||
                $iterable instanceof stdClass
        ) {
            return $iterable;
        }

        throw $this->_createInvalidArgumentException(
            $this->__('Invalid iterable'),
            null,
            null,
            $iterable
        );
    }