ize_values( $items );
	}

	/**
	 * Unserialize item values.
	 *
	 * @param array $items Events from the Queue to be serialized.
	 *
	 * @return mixed
	 */
	private function unserialize_values( $items ) {
		array_walk(
			$items,
			function ( $item ) {
				$item->value = maybe_unserialize( $item->value );
			}
		);

		return $items;

	}

	/**
	 * Return true if the buffer is still valid or an Error other wise.
	 *
	 * @param Automattic\Jetpack\Sync\Queue_Buffer $buffer The Queue_Buffer.
	 *
	 * @return bool|\WP_Error
	 */
	private function validate_checkout( $buffer ) {
		if ( ! $buffer instanceof Queue_Buffer ) {
			return new \WP_Error( 'not_a_buffer', 'You must checkin an instance of Automattic\\Jetpack\\Sync\\Queue_Buffer' );
		}

		$checkout_id = $this->get_checkout_id();

		if ( ! $checkout_id ) {
			return new \WP_Error( 'buffer_not_checked_out', 'There are no checked out buffers' );
		}

		// TODO: change to strict comparison.
		if ( $checkout_id != $buffer->id ) { // phpcs:ignore WordPress.PHP.StrictComparisons.LooseComparison
			return new \WP_Error( 'buffer_mismatch', 'The buffer you checked in was not checked out' );
		}

		return true;
	}
}