Code review comment for lp:~aaronp/rnr-server/get-usefulness-by-user

I'm re-thinking the patch now. Is this a better way?

> @validate('review_id', int, required=False)
> @validate_pattern('username', r'[^\n]+', required=False)
> @returns_json
> def get_usefulness(self, review_id=None, username=None):
> """Get a list of usefulness filtered by username/review_id"""
> if not username and not review_id:
> return None
>
> data = {}
> if username:
> data ['username'] = username
> if review_id:
> data ['review_id'] = str(review_id)
>
> return self._get('/usefulness/%s' % get_string, data=data,
> scheme=PUBLIC_API_SCHEME)