code: def guess_mime (filename):
      
      mime, encoding = guess_mime_file(filename)
      if mime is None:
          mime, encoding = guess_mime_mimedb(filename)
      assert mime is not None or encoding is None
      return mime, encoding
docs: Guess the MIME type of given filename using file(1) and if that
      fails by looking at the filename extension with the Python mimetypes
      module.
  
      The result of this function is cached.