def METHOD_NAME(self):
    fmt = string.Formatter()
    self.assertEqual(fmt.format("-{arg}-", arg='test'), '-test-')
    self.assertRaises(KeyError, fmt.format, "-{arg}-")
    self.assertEqual(fmt.format("-{self}-", self='test'), '-test-')
    self.assertRaises(KeyError, fmt.format, "-{self}-")
    self.assertEqual(fmt.format("-{format_string}-", format_string='test'),
                     '-test-')
    self.assertRaises(KeyError, fmt.format, "-{format_string}-")
    self.assertEqual(fmt.format(arg='test', format_string="-{arg}-"),
                     '-test-')