def serverGreeting(self, greeting):
        """
        Handle the server greeting.

        @type greeting: L{bytes}
        @param greeting: The server greeting minus the status indicator.
            For servers implementing APOP authentication, this will contain a
            challenge string.
        """

        Handle the server greeting.

        @type greeting: L{bytes}
        @param greeting: The server greeting minus the status indicator.
            For servers implementing APOP authentication, this will contain a
            challenge string.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/pop3client.py