How to use the filetype.guess_extension function in filetype

def test_guess_extension_buffer_invalid(self):
        buf = bytearray([0xFF, 0x00, 0x00, 0x00, 0x00])
        ext = filetype.guess_extension(buf)
        self.assertTrue(ext is None)

def test_guess_extension_file_path(self):
        ext = filetype.guess_extension(FIXTURES + '/sample.jpg')
        self.assertTrue(ext is not None)
        self.assertEqual(ext, 'jpg')

def test_guess_extension_buffer(self):
        buf = bytearray([0xFF, 0xD8, 0xFF, 0x00, 0x08])
        ext = filetype.guess_extension(buf)
        self.assertTrue(ext is not None)
        self.assertEqual(ext, 'jpg')

def test_guess_extension_memoryview(self):
        buf = memoryview(bytearray([0xFF, 0xD8, 0xFF, 0x00, 0x08]))
        ext = filetype.guess_extension(buf)
        self.assertTrue(ext is not None)
        self.assertEqual(ext, 'jpg')

def upload_image():
    _clear_imagemagick_temp_files()

    if "file" not in request.files:
        return jsonify(error="File is missing!"), 400

    file = request.files["file"]

    random_string = _get_random_filename()
    tmp_filepath = os.path.join("/tmp/", random_string)
    file.save(tmp_filepath)
    output_type = settings.OUTPUT_TYPE or filetype.guess_extension(tmp_filepath)
    error = None

    output_filename = os.path.basename(tmp_filepath) + f".{output_type}"
    output_path = os.path.join(settings.IMAGES_DIR, output_filename)

    try:
        with Image(filename=tmp_filepath) as img:
            img.strip()
            if output_type not in ["gif"]:
                with img.sequence[0] as first_frame:
                    with Image(image=first_frame) as first_frame_img:
                        with first_frame_img.convert(output_type) as converted:
                            converted.save(filename=output_path)
            else:
                with img.convert(output_type) as converted:
                    converted.save(filename=output_path)