def deleteMessage(index):
        """
        Mark a message for deletion.

        This must not change the number of messages in this mailbox.  Further
        requests for the size of the deleted message should return 0.  Further
        requests for the message itself may raise an exception.

        @type index: L{int}
        @param index: The 0-based index of a message.

        @raise ValueError or IndexError: When the index does not correspond to
            a message in the mailbox.  The use of ValueError is preferred.
        """

        Mark a message for deletion.

        This must not change the number of messages in this mailbox.  Further
        requests for the size of the deleted message should return 0.  Further
        requests for the message itself may raise an exception.

        @type index: L{int}
        @param index: The 0-based index of a message.

        @raise ValueError or IndexError: When the index does not correspond to
            a message in the mailbox.  The use of ValueError is preferred.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/interfaces.py