运行docker-compose up时出现以下错误：

ERROR: The Compose file './docker-compose.yml' is invalid because:
Invalid top-level property "wordpress". Valid top-level sections for this Compose file are: version, services, networks, volumes, and extensions starting with "x-".

You might be seeing this error because you're using the wrong Compose file version. Either specify a supported version (e.g "2.2" or "3.3") and place your service definitions under the `services` key, or omit the `version` key and place your service definitions at the root of the file to use version 1.
For more on the Compose file format versions, see https://docs.docker.com/compose/compose-file/

基础架构详细信息：

• 多克尔

Docker version 23.0.0, build e92dd87

• docker-compose（使用apt-get install docker-compose安装）

docker-compose version 1.25.0, build unknown

docker-compose.yml

version: '3'

wordpress:
  image: wordpress
  links:
    - db:mysql

db:
  image: mariadb
  environment:
    MYSQL_ROOT_PASSWORD: '<a secure password>'