self.assertEqual(mimetype2ext('text/vtt'), 'vtt')
         self.assertEqual(mimetype2ext('text/vtt;charset=utf-8'), 'vtt')
         self.assertEqual(mimetype2ext('text/html; charset=utf-8'), 'html')
         self.assertEqual(mimetype2ext('text/vtt'), 'vtt')
         self.assertEqual(mimetype2ext('text/vtt;charset=utf-8'), 'vtt')
         self.assertEqual(mimetype2ext('text/html; charset=utf-8'), 'html')