def METHOD_NAME(self):
    delta = timezone.timedelta(hours=1, minutes=30, seconds=15)
    self.assertEqual(
        duration.duration_string(delta), "1 hour, 30 minutes, 15 seconds"
    )
    self.assertEqual(duration.duration_string(delta, "m"), "1 hour, 30 minutes")
    self.assertEqual(duration.duration_string(delta, "h"), "1 hour")
    self.assertEqual(duration.duration_string(""), "")
    self.assertRaises(TypeError, duration.duration_string("not a delta"))