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