The team are currently review the experimental additions to l3kernel
which are defined in l3candidates. As part of that process, we are
moving the following to 'stable' status
We are also adding the new function
This replaces the experimental \prop_get:Nn, which is therefore
deprecated and will be removed from expl3 at the end of 2015.
These changes will be present in the next expl3 release, likely to take
place this weekend.