def METHOD_NAME(self):
    expected = set('*')
    self.assertIs(type(Protein.stop_chars), set)
    self.assertEqual(Protein.stop_chars, expected)
    Protein.stop_chars.add("JO")
    self.assertEqual(Protein.stop_chars, expected)
    self.assertEqual(Protein('').stop_chars, expected)
    with self.assertRaises(AttributeError):
        Protein('').stop_chars = set("^&")