为selenium集线器节点设置maxSessions & maxInstances的正确的docker-compose yml是什么？

version: '3'
services:
  selenium-hub:
    image: selenium/hub
    ports:
      - "4444:4444"
  chrome-node:
    image: selenium/node-chrome
    depends_on:
      - selenium-hub
    environment:
      - HUB_HOST=selenium-hub
      - HUB_PORT=4444
      - maxSessions=5
      - maxInstances=5
  firefox-node:
    image: selenium/node-firefox
    depends_on:
      - selenium-hub
    environment:
      - HUB_HOST=selenium-hub
      - HUB_PORT=4444
      - maxSessions=5
      - maxInstances=5