Any McGraphObj-derived interface (e.g., McGraphObjRect) can be added. The added graph object does not have to be linked to our Parent McFeatures instance, nor does it have to have any particular McGraphOverlay. This allows you to add graph objects to the collection for convenient group manipulation.
The McFeatures.DisplayObjects collection will be initially empty if you pass in the mcdoDoNotPopulate flag as the mcdoFlags argument.