Why does unittest's `mock.patch.start` re-run the function in which the patcher is started?

Let's say we have two files:

to_patch.py

from unittest.mock import patch

def patch_a_function():
    print("Patching!")
    patcher = patch("to_be_patched.function")
    patcher.start()
    print("Done patching!")

to_be_patched.py

from to_patch import patch_a_function

def function():
    pass

patch_a_function()
function()

And we run python -m to_be_patched. This will output:

Patching!
Patching!

1. Why isn't Done patching! ever printed?
2. Why is Patching! printed twice?

I've narrowed the answer to (2) down; the call to patch.start seems to trigger patch_a_function again. I suspect this is because it's imported in to_be_patched.py, but am not sure why the function itself would run for a second time. Similarly, I'm not sure why the Done patching! line is not reached in either of the calls to patch_a_function. patcher.start() can't be blocking, because the program exits nicely instead of hanging there... right?

from Why does unittest's `mock.patch.start` re-run the function in which the patcher is started?