I am using lockfile library which is unmaintained. I want to switch to filelock but this package is missing the PIDLockFile capability.
It's a simple capability of allowing to take a lock on a pid from a pid file.
I think that you can even copy-paste the class code from lockfile as license permit it?
The source code of the class can be viewed with

import inspect
from lockfile.pidlockfile import PIDLockFile

print(inspect.getsource(PIDLockFile))