How to get the extras that have been installed?

[R5dan]

If my package is installed, how can I tell which (if any) extras have been installed.

If my extras are like:

extras_require = {
    "dev":[],
    "docs":[],
    "extra":[] # etc
}

and it is installed like pip install "package[dev, docs]" how can I get that dev and docs has been installed and not extra (even if they have the same packages)?