def getMessage(index):
        """
        Retrieve a file containing the contents of a message.

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

        @rtype: file-like object
        @return: A file containing the message.

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

        Retrieve a file containing the contents of a message.

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

        @rtype: file-like object
        @return: A file containing the 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