webapp2_extras.sessions.SessionDict.__slots__ and SessionDict.container are unused?

```
If the following are unused, should they be removed?

- webapp2_extras.sessions.SessionDict.__slots__ 
- webapp2_extras.sessions.SessionDict.container
```

Original issue reported on code.google.com by `chriswil...@gmail.com` on 22 Apr 2014 at 2:36
