what is wrong with this yaml file

version: '3.3'
services:
  portainer-ce:
    ports:
      - '9000:9000'
      - '8000:8000'
  container_name: portainer
  networks:
    - nginxproxymanager_default
  restart: always
  volumes:
    - '/var/run/docker.sock:/var/run/docker.sock'
    - '/home/docker/portainer:/data'
  image: 'portainer/portainer-ce:latest'
networks:
  nginxproxymanager_default:
    external: true

Keep getting error container_name’ must be a mapping not a string