code: public static String getFormatFromXmlFile(File xmlFile) {
          if (xmlFile == null || !xmlFile.exists())
              return null;
  
          try (Reader reader = createReader(xmlFile)) {
              return getFormatFromXmlReader(reader);
          }
          catch (IOException | RuntimeException e) {
              return null;
          }
      }
docs: Returns the NAACCR format of the given XML file.
  @param xmlFile provided data file
  @return the NAACCR format, null if it cannot be determined