MAG4 INDEX GET TYPE    ICR (5560)

Used to filter out those image types that belong to a
given image category (Class). When images are displayed, it is desirable to
limit the list of presented images to only those that are likely to be
relevant in the current context.

This procedure accepts an "image class" (either an IEN or the name of a class)
and returns all "image types" that belong to that class.