public static function toProtobuf($object, $filter = NULL)
	{
		$output = '';

		if (isset($object->x) && ($filter === null || isset($filter['x']))) {
			$output .= "\x0a";
			$buffer = EmbeddedMeta::toProtobuf($object->x, $filter === null ? null : $filter['x']);
			$output .= Binary::encodeVarint(strlen($buffer));
			$output .= $buffer;
		}

		return $output;
	}