def test_mailboxWithoutNamespace(self):
        """
        A mailbox that does not provide L{INamespacePresenter} returns
        empty L{list}s for its personal, shared, and user namespaces.
        """
        self.server.theAccount = AccountWithoutNamespaces(b'testuser')
        self.namespaceArgs = None
        def login():
            return self.client.login(b'testuser', b'password-test')
        def namespace():
            def gotNamespace(args):
                self.namespaceArgs = args
                self._cbStopClient(None)
            return self.client.namespace().addCallback(gotNamespace)

        d1 = self.connected.addCallback(strip(login))
        d1.addCallback(strip(namespace))
        d1.addErrback(self._ebGeneral)
        d2 = self.loopback()
        d = defer.gatherResults([d1, d2])
        d.addCallback(lambda _: self.namespaceArgs)
        d.addCallback(self.assertEqual, [[], [], []])
        return d

        A mailbox that does not provide L{INamespacePresenter} returns
        empty L{list}s for its personal, shared, and user namespaces.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py