I think `Image` and `Folder` are misleading as a first example, since those require additional setup to work as expected. The filesystem vs. DataObjects has always been weird and not well understood in SilverStripe, so I think its counterproductive here. How about just sticking to a fictional example with just the essentials? How about this:

```yml
Player:
  john:
    Name: John
  joe:
    Name: Joe
  jack:
    Name: Jack
Team:
  hurricanes:
    Name: The Hurricanes
    Origin: Wellington
    Players: =>Player.john
  crusaders:
    Name: The Crusaders
    Origin: Bay of Plenty
    Players: =>Player.joe,=>Player.jack
```