Mojones-master this adds to #398

[drvinceknight]

This PR simply adds a couple of commits to @mojones's #398 merging this would automatically merge in #398 (because github is cool).

This really only needs to be ok'd by @marcharper as #398 has gone through a detailed review by him and I. This is a minor review change:

• Adding an example to docstring
• Fixing a test (unless I'm mistaken the previous version was not running one set of tests)
• Changing something back to string notation for clarity (Marc: you might well have had a reason for changing this).

[marcharper]

Looks fine to me!

[meatballs]

and there we have it!