code: protected function accountNumber($text)
      {
          $format = $this->format == self::FORMAT_CLASSIC ? '/^[0-9.]+/' : '/^[0-9A-Z]+/';
          if ($account = $this->getLine('25', $text)) {
              if (preg_match($format, $account, $match)) {
                  return str_replace('.', '', $match[0]);
              }
          }
  
          return null;
      }
docs: Parse an account number
  
  @param string $text Statement body text
  @return string|null