This is causing the documentation build to fail.  If you look at http://docs.astropy.org/en/latest/development/docrules.html#sections (under 8. see also), it shows how to use this - you don't use the backticks, but rather just name the function.  I *think* you can also get away with just doing `angle_utilities.angular_separation` instead of the full name, but you should probably check that.