Okay, I think I understand this now. `build_statuses` actually has 7 keys. `issue_num`, and then a key for each downstream build. Is that correct? Does redis-brain support nested dictionaries? I would like to do something like this instead, but it would only work if nested dictionaries are supported:

```
build_data = robot.brain.get(upstream_build_num) or {} 
build_data['issue_num'] = params.ISSUE
build_statuses = build_data.get('statuses') or {}
build_statuses[project] = build_status
build_data['statuses'] = build_statuses

num_builds = Object.keys(build_statuses).length
```