How do you understand python "lock cquisition can now be interrupted by signals on POSIX" in its documentation?

I found the following description in python threading documentation:

Changed in version 3.2: Lock acquisition can now be interrupted by signals on POSIX if the underlying threading implementation supports it.

What does it mean?

1. Does it mean that when I acquire a lock with "blocking=True", I can find this "lock acquisition" operation via some operating system tool, and then cancel it by sending a specific SIGNAL to the Python thread?
2. Or does it mean that specifying "timeout=x" will need that so called "signal" to interrupt it?

If "1" is correct, then how can I find the acquisition operation and how can I send the signal to stop it? If "2" is correct, does it mean that the "timeout=x" will not work if I'm using a system that doesn't support it, and what are those systems?

Python documentation:

https://docs.python.org/3/library/threading.html#lock-objects