Get the state of a map, and subscribe for updates

Hi

I'm wondering if there is any way around the following code to get the state of a map, and subscribe for updates:

```
for t in self._mymap.values(predicate):
on_update(t)

registration_id = self._mymap.add_entry_listener(include_value=True,
added_func=on_update,
predicate=predicate)
```

In particular, how to avoid a race condition here?