code: public Map<List<String>, String> extractNestedTypes(XEvent event) {
  		return XCostType.instance().extractNestedValues(event);
  	}
docs: Retrieves a map containing all cost types for all descending attributes
  of an event.
  
  @see #extractNestedAmounts(XEvent)
  
  @param event
  Event to retrieve all cost types for.
  @return Map from all descending keys to cost types.