vRA Property Groups

Using a script component in vRO and the vRA plugin I can get a list of custom properties for a composite blueprint using vCACCAFE:CompositeBlueprint.properties.  And I can get the list of property groups for a blueprint using vCACCAFE:CompositeBlueprint.propertyGroups.  But I can't figure out how to get a list of properties from a property group.

I can't find any scripting classes or methods for a vRA property group.  How can I get the list of properties included in a property group?