Why does the main image depend on the `python` meta-package?

[make-github-pseudonymous-again]

I see here that the main Dockerfile depends on both python and python3. Can you explain why?

https://github.com/zodern/meteor-docker/blob/7c2cc7090bb58b5cb86f9a4d6724657b169b1b67/image/Dockerfile#L4

python seems to be a "meta" package or package "group" which brings in multiple dependencies (python2, ...). Why do we need both python2 and python3? Why can't we list the python2 package explicitly instead?