code: public <T> PropertyKey<T> getDirectAccessReferenceGroup(String name, Class<T> type) {
  
  		if (!propertyKeys.containsKey(name)) {
  			throw new IllegalArgumentException("ReferenceGroup " + dbName + " does not contain grouped property " + name + "!");
  		}
  
  		return new GenericProperty(propertyKeys.get(name).dbName());
  	}
docs: Returns a wrapped group property that can be used to access a nested group
  property directly, i.e. without having to fetch the group first.
  
  @param <T>
  @param name
  @param type
  @return property