I have a Flask app running behind Apache HTTPD. Apache is configured to have multiple child processes.

The Flask app creates a file on the server with the file's name equal to its process ID.
The code looks something like this:

```
import os

@app.before_first_request
def before_first_request():
    filename = os.getpid()
    with open(filename, 'w') as file:
        file.write('Hello')

```

When the child process is killed/ended/terminated I would like the Flask app to remove this file. 

It's not terribly important that removal of a file happens, as these files won't take up much space, so if bizarre errors occur I don't need to handle them. But for normal workflow, I would like to have some cleanup when Apache shuts down the Flask process.

Any idea on the best way to do this?