How's the #'id property used

[Ewald Liska]

Hi all,

may I ask how the 'id property defined in grob-interface is actually used?

I can assign it a value using

{
  c'
  \once \override NoteHead.id = "Hi, I'm an ID"
  d' e'
}

and it will show up properly in the resulting SVF file. But is that
property actually used somewhere already or it is just provided in order
to be set by users?

Urs