An example code snippet to detect if the API supports the new parameter at runtime for code that wants to use to use something other than the default '&'.

```
if 'separator' in inspect.signature(urllib.parse.parse_qs).parameters:
    ... parse_qs(..., separator=';')
else:
    ... parse_qs(...)
```

calling it with the arg and catching TypeError if that fails would also work, but might not be preferred as catching things like TypeError is non-specific and could hide other problems, making it a code maintenance headache.