code: private Object loadObjectFromTemporary(String fieldname, String complete) throws Exception {
          String realName = fieldname.substring(1);
          if (!temporaryFields.containsKey(realName)) {
              String message = String.format("The temporary field %s doesn't exist.", complete);
              throw new IllegalArgumentException(message);
          }
          return temporaryFields.get(realName);
      }
docs: Loads the object for the given field name from the temporary fields. If an error occurs, the complete path
  (inclusive nested names) are given in an exception.