public Map<String, String> getFlattened() {
    final TreeMap<String, String> returnVal = new TreeMap<>();
    returnVal.putAll(getMapByPrefix(""));
    return returnVal;
  }
Returns a map of all the flattened properties, the item in the returned map is sorted
alphabetically by the key value.

@Return
dss-appconn/appconns/dss-eventchecker-appconn/src/main/java/com/webank/wedatasphere/dss/appconn/eventchecker/utils/Props.java