def addListener(listener):
        """
        Add a mailbox change listener

        @type listener: Any object which implements C{IMailboxIMAPListener}
        @param listener: An object to add to the set of those which will be
            notified when the contents of this mailbox change.
        """

        Add a mailbox change listener

        @type listener: Any object which implements C{IMailboxIMAPListener}
        @param listener: An object to add to the set of those which will be
            notified when the contents of this mailbox change.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/interfaces.py