Core Audio Server PlugIn - What is kAudioBoxPropertyHasMIDI For?

I am trying to determine how to best implement MIDI for an audio device box that has both audio and MIDI. I noticed the kAudioBoxPropertyHasMIDI property listed in the NullAudio sample. But I haven't found any info about the significance of the property. Ideally, I would like my Core Audio Server Plugin to have MIDI routed to and from it as it has access to the hardware. Any advice is much appreciated.
Core Audio Server PlugIn - What is kAudioBoxPropertyHasMIDI For?
 
 
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