def test_opt_charsetWithRemainder(self):
        """
        A line that has additional data after a C{CHARSET} identifier
        is parsed as that identifier, and the remainder is that
        additional data.
        """
        line = b"CHARSET UTF-8 remainder"
        identifier, remainder = self.server.opt_charset(line)
        self.assertEqual(identifier, b"UTF-8")
        self.assertEqual(remainder, b"remainder")

        A line that has additional data after a C{CHARSET} identifier
        is parsed as that identifier, and the remainder is that
        additional data.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py