code: public <T> PropertyKey<T> getNestedProperty(String name, Class<T> type) {
  
  		if (!propertyKeys.containsKey(name)) {
  			throw new IllegalArgumentException("ReferenceGroup " + dbName + " does not contain grouped property " + name + "!");
  		}
  
  		return propertyKeys.get(name);
  	}
docs: Returns the nested group property for the given name. The PropertyKey returned by
  this method can be used to get and/or set the property value in a PropertyMap that
  is obtained or stored in the group property.
  
  @param <T>
  @param name
  @param type
  @return property