How do I pull the parent.sys_class_name in a query?

Hello,

I am trying to get a count of the parent.sys_class_name in the cmdb_rel_ci table but I do not understand why the script is not working.   I used this script previously to just pull sys_class_name from a different table and it had worked so I am not sure why parent.sys_class_name is not working.

Any ideas?

//count number of server instances grouped by sys class name
var agg = new GlideAggregate('cmdb_rel_ci');
agg.addAggregate('COUNT', 'parent.sys_class_name');
agg.groupBy('parent.sys_class_name');
agg.query();
while (agg.next()) {
   var serverType = agg.parent.sys_class_name.getDisplayValue();
   var hierarchy = new GlideRecord('u_land_o_lakes_physical_servers_allocation');
   hierarchy.addQuery('u_allocate_to',serverType);
   hierarchy.query();
   var getCount = agg.getAggregate('COUNT', 'parent.sys_class_name');
   if (hierarchy.next()) {
   hierarchy.u_allocate_to = serverType;
   hierarchy.update();
   } else {
   hierarchy.u_allocate_to = serverType;
   hierarchy.insert();
   }
}