code: private void updateUnknownStatus(Map<String, Map<String, String>> statusMap,
        List<String> unreportedNn) {
      if (unreportedNn == null || unreportedNn.isEmpty()) {
        // no unreported namenodes
        return;
      }
      
      for (Map.Entry<String, Map<String,String>> entry : statusMap.entrySet()) {
        String dn = entry.getKey();
        Map<String, String> nnStatus = entry.getValue();
        for (String nn : unreportedNn) {
          nnStatus.put(nn, DecommissionStates.UNKNOWN.toString());
        }
        statusMap.put(dn, nnStatus);
      }
    }
docs: update unknown status in datanode status map for every unreported namenode