code: public void assignTypes(XTrace trace, Map<List<String>, String> types) {
  		XCostType.instance().assignNestedValues(trace, types);
  	}
docs: Assigns (to the given trace) multiple cost types given their keys.
  Note that as a side effect this method
  creates attributes when it does not find an attribute with the proper
  key.
  
  @see #assignAmounts(XTrace, Map)
  
  @param trace
  Trace to assign the cost types to.
  @param types
  Mapping from keys to cost types which are to be assigned.