docs: def detect_file(filename):
      """Decide what to do with the file."""
      image_format = get_image_format(filename)
  
      if image_format in Settings.formats:
          return image_format
  
      if image_format in (NONE_FORMAT, ERROR_FORMAT):
          return None
  
      if Settings.verbose > 1 and not Settings.list_only:
          print(filename, image_format, 'is not a enabled image or '
                'comic archive type.')
      return None