nginx-wsgi-flask unused exposed port?

[skwzrd]

What is this exposed port used for? There is no reference to it elsewhere. I ran sudo docker compose up -d without it and it works fine.

https://github.com/docker/awesome-compose/blob/e6b1d2755f2f72a363fc346e52dce10cace846c8/nginx-wsgi-flask/flask/Dockerfile#L30