Restrictions

   o  You cannot delete generation 1 of an element.
   o  You cannot delete a generation that has variants off it.
   o  You cannot delete a generation that has a review pending.
   o  You cannot delete a generation that is reserved.
   o  You cannot delete a generation that is in a class.
   o  All generations in the specified range of generations to be
      deleted must be on the same line of descent.
   o  You cannot use /GENERATION in combination with /AFTER, /BEFORE,
      /FROM, or /TO.
   o  You cannot specify /AFTER and /FROM on the same command line.
   o  You cannot specify /BEFORE and /TO on the same command line.