Get an individual :class:`MacMailMessage` within a Mail
        data file, based on size and offset information from the
        corresponding :class:`MacIndexMessage`.

        :param offset: offset within the Mail file where the desired
            message begins, i.e. :attr:`MacMailMessage.offset`
        :param size: size of the message,
            i.e. :attr:`MacMailMessage.size`

def get_message(self, offset, size):
        '''Get an individual :class:`MacMailMessage` within a Mail
        data file, based on size and offset information from the
        corresponding :class:`MacIndexMessage`.

        :param offset: offset within the Mail file where the desired
            message begins, i.e. :attr:`MacMailMessage.offset`
        :param size: size of the message,
            i.e. :attr:`MacMailMessage.size`
        '''
        return MacMailMessage(size=size, mm=self.mmap, offset=offset)