Extending Configurable Containers
Some configurable traits are containers (list, dict, set) Config objects now support calling extend, update, insert, etc. on traits in config files, which will ultimately result in calling those methods on the original object.
The effect being that you can now add to containers without having to copy/paste the initial value:
c = get_config() c.InlineBackend.rc.update({ 'figure.figsize' : (6, 4) })