thanks!

In that case, I am not going to merge this into master for a 4.x release. The next blacklight_advanced_search release that will still work with BL 4.x will not have this, and will produce deprecation warnings in 4.7, so it goes. Because I want it to be able to work on any BL 4.x. 

The release after that for BL 5.x will have this in there (becuase this is already merged into blacklight5 branch I think). 

Feel free to let me know if you think there's a better way to do it!