The location of #prefix has changed, but it looks like it might not be getting called, judging by the specs below?  For example, the spec now reads:

```ruby
@obj.fields.keys.should include(:related_url)
```
rather than
```ruby
@obj.fields.keys.should include(:my_datastream__related_url)
```

This isn't a problem in some apps, but what happens when you have multiple datastreams that define a title?