docs: public List<String> getAncestorDNs(String DN, int level) throws WIMException {
          if (DN == null || DN.trim().length() == 0) {
              return null;
          }
          try {
              NameParser nameParser = getNameParser();
              Name name = nameParser.parse(DN);
              int size = name.size();
  
              List<String> ancestorDNs = new ArrayList<String>();
              if (level == 0) {
                  level = size;
              }
  
              for (int i = size - 1; i >= (size - level); i--) {
                  name.remove(i);
                  ancestorDNs.add(name.toString());
              }
              return ancestorDNs;
          } catch (NamingException e) {
              String msg = Tr.formatMessage(tc, WIMMessageKey.NAMING_EXCEPTION, WIMMessageHelper.generateMsgParms(e.toString(true)));
              throw new WIMSystemException(WIMMessageKey.NAMING_EXCEPTION, msg, e);
          }
      }