def test_searchNot(self):
        """
        L{imap4.IMAP4Server.search_NOT} returns the negation of the result
        of the expression supplied to it.
        """
        self.assertFalse(self.server.search_NOT(
                ["SENTSINCE"] + self.earlierQuery, self.seq, self.msg,
                (None, None)))
        self.assertTrue(self.server.search_NOT(
                ["SENTON"] + self.laterQuery, self.seq, self.msg,
                (None, None)))

        L{imap4.IMAP4Server.search_NOT} returns the negation of the result
        of the expression supplied to it.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py