code: private String getCheckstyleVersion() {
          Package checkstyleApiPackage = Configuration.class.getPackage();
  
          return (checkstyleApiPackage == null) ? null : checkstyleApiPackage.getImplementationVersion();
      }
docs: Get the effective Checkstyle version at runtime.
  
  @return the MANIFEST implementation version of Checkstyle API package (can be <code>null</code>)
  @todo Copied from CheckstyleReportGenerator - move to a utility class