I'm not able to figure out how to get the line 3.5mm audio jack on the new MacBook Pro to act as a line in port. This is a non-touch bar 13" MacBook Pro. I do remember reading that they dropped the optical out from this port, but was under the impression that it was still possible to use this port as a line in. I'm plugging in a stereo 3.5mm plug from a line out from a mixer. But when I pull up the sound input options in systems preferences, it only lets me select internal mic as the option. Is this no longer possible on a MBP?