So the correct solution is really to pre-approve dependencies and store them in a local PyPi. Defence, Medical and some other high-sec industries do this as a matter of course. The problem with this approach is the amount of security toil required to vet packages is large, generally too large for most companies to buy into.

So one solution I see in the wild a lot is to prefix your company packages with a company identifier, then to set proxy rules to prevent fetching these from public PyPi (often these are set directly on the private PyPi and all traffic is directed through it).

Having been an agency pentester, I can tell you that given access to one company package (Open Sourced?), you can correctly guess the package structure, naming conventions and internal build infra of the company 90+% of the time.