docs: def addClassKey(self, klass, key, obj):
          """
          Adds an object to the collection, based on klass and key.
  
          @param klass: The class of the object.
          @param key: The datastore key of the object.
          @param obj: The loaded instance from the datastore.
          """
          d = self._getClass(klass)
  
          d[key] = obj