code: public static function checkErrorCode($pValue)
      {
          $pValue = (string) $pValue;
  
          if (!isset(self::$errorCodes[$pValue])) {
              $pValue = '#NULL!';
          }
  
          return $pValue;
      }
docs: Check a value that it is a valid error code.
  
  @param mixed $pValue Value to sanitize to an Excel error code
  
  @return string Sanitized value