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