def authenticateUserAPOP(self, user, digest):
        """
        Authenticate against a user against a virtual domain.

        @param user: The username.
        @param digest: The digested password.

        @return: A three-tuple like the one returned by
            L{IRealm.requestAvatar}.  The mailbox will be for the user given
            by C{user}.
        """
        user, domain = self.lookupDomain(user)
        return self.service.domains[b'baz.com'].authenticateUserAPOP(
            user, digest, self.magic, domain)

        Authenticate against a user against a virtual domain.

        @param user: The username.
        @param digest: The digested password.

        @return: A three-tuple like the one returned by
            L{IRealm.requestAvatar}.  The mailbox will be for the user given
            by C{user}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_pop3.py