public void storeFlattened(final File file) throws IOException {
    final BufferedOutputStream out =
        new BufferedOutputStream(new FileOutputStream(file));
    try {
      storeFlattened(out);
    } finally {
      out.close();
    }
  }
Store all properties, those local and also those in parent props

@param file The file to store to
@throws IOException If there is an error writing
dss-appconn/appconns/dss-eventchecker-appconn/src/main/java/com/webank/wedatasphere/dss/appconn/eventchecker/utils/Props.java