Referencing keys of objects in db.Models

The Google App Engine revolves around keys. If you have references to other objects within your Models, it is important to understand the consequence of accessing the model (to prevent fetch statements). In particular, if you only need to Key of the item (or an attribute on the Key such as the id()) then you want to avoid inflating the persistable. There are numerous suggestions on how to accomplish this. Squeeville posted a nice short explaination of how to do it here.