menpo/menpo — pull request #359 by patricksnape (2014-05-19 17:46:26+00:00)
Title: Landmark upgrades

This adds two very simple concepts to landmarks:

- You can now delete from `LandmarkManager`
`del image.landmarks['label']`
- Iterating over `LandmarkManager` now only returns the keys

```
for label in image.landmarks:
image.landmarks[label] # Access like this
```
- This has the added bonus that you can now do
`assert ('label' in landmarks)`
- Similarly, for `LandmarkGroup`, you can delete a label:
`del image.landmarks['label']['leye']`
However, it comes with a caveat. If you try to delete a label that leaves a point unlabelled, this **will throw an exception**. This maintains the current interface for `LandmarkGroup` in that you can't have a `LandmarkGroup` that has unlabelled points.