def expunge():
        """
        Remove all messages flagged \\Deleted.

        @rtype: L{list} or L{Deferred}
        @return: The list of message sequence numbers which were deleted, or a
            L{Deferred} whose callback will be invoked with such a list.

        @raise ReadOnlyMailbox: Raised if this Mailbox is not open for
            read-write.
        """

        Remove all messages flagged \Deleted.

        @rtype: L{list} or L{Deferred}
        @return: The list of message sequence numbers which were deleted, or a
            L{Deferred} whose callback will be invoked with such a list.

        @raise ReadOnlyMailbox: Raised if this Mailbox is not open for
            read-write.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/interfaces.py