code: protected function statementBody($text)
      {
          switch (substr($this->getLine('20', $text), 0, 4)) {
              case '940A':
                  $this->format = self::FORMAT_CLASSIC;
                  break;
              case '940S':
                  $this->format = self::FORMAT_STRUCTURED;
                  break;
              default:
                  throw new \RuntimeException('Unknown file format');
          }
  
          return parent::statementBody($text);
      }
docs: Determine the format for this statement
  
  @param string $text Statement body text
  @return \Jejik\MT940\Statement