def test_exists(self):
        """
        If the server response to a I{SELECT} or I{EXAMINE} command includes an
        I{EXISTS} response, the L{Deferred} return by L{IMAP4Client.select} or
        L{IMAP4Client.examine} fires with a C{dict} including the value
        associated with the C{'EXISTS'} key.
        """
        d = self._examineOrSelect()
        self._response(b'* 3 EXISTS')
        self.assertEqual(
            self.successResultOf(d),
            {'READ-WRITE': False, 'EXISTS': 3})

        If the server response to a I{SELECT} or I{EXAMINE} command includes an
        I{EXISTS} response, the L{Deferred} return by L{IMAP4Client.select} or
        L{IMAP4Client.examine} fires with a C{dict} including the value
        associated with the C{'EXISTS'} key.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py