code: public function guess(string $path): string
      {
          if (!is_file($path)) {
              throw new FileNotFoundException($path);
          }
  
          if (!is_readable($path)) {
              throw new AccessDeniedException($path);
          }
  
          if (0 == count($this->guesserList)) {
              $msg = 'Unable to guess the mime type as no guessers are available';
              if (!FileInfoMimeType::isSupported()) {
                  $msg .= ' (Did you enable the php_fileinfo extension?)';
              }
              throw new \LogicException($msg);
          }
  
          /** @var FileInfoMimeType|BinaryMimeType $guesser */
          foreach ($this->guesserList as $guesser) {
              if ('' != $mimeType = $guesser->guess($path)) {
                  return $mimeType;
              }
          }
  
          return '';
      }
docs: Get mime type or NULL, if none could be guessed.
  
  @param string $path Path to the file
  @return string
  @throws \LogicException
  @throws FileNotFoundException
  @throws AccessDeniedException