feedback better unload

addon/-private/system/model/internal-model.js

@@ -297,6 +297,18 @@ InternalModel.prototype = {
     return array;
   },
 
+  /**
+    Unload the record for this internal model.  This will cause the record to be
+    destroyed and freed up for garbage collection.  It will also trigger a check
+    for cleaning up internal models.
+
+    This check is performed by first computing the set of related internal
+    models.  If all records in this set are unloaded, then the entire set is
+    destroyed.  Otherwise, nothing in the set is destroyed.
+
+    This means that this internal model will be freed up for garbage collection
+    once all models that refer to it via some relationship are also unloaded.
+  */
   unloadRecord() {
     this.send('unloadRecord');
     this.dematerializeRecord();