Unable to double top level function when called through a func set dict.

I see this pattern often enough in Python:

```python
available_adapters = {
  'cookie_adapter': cookie_adapter
}

def cookie_adapter(yom):
    pass

def do_stuff(args):
    if "cookie_adapter" in available_adapters:
        available_adapters["cookie_adapter"](*args)
```

Unfortunately when I try to `allow` cookie_adapter to be called, doubles fails to step in when the subsequent call to `do_stuff` occurs.

I've created a basic test to try and prove out the failure. Let me know if I can help in any way :)