Given a message number that we found with imap_search,
        get the text/plain content.
        @Params
        msg_nums - message number to get message for
        @Returns
        Plaintext content of message matched by message number

def fetch_plaintext(self, msg_nums):
        """
        Given a message number that we found with imap_search,
        get the text/plain content.
        @Params
        msg_nums - message number to get message for
        @Returns
        Plaintext content of message matched by message number
        """
        if not msg_nums:
            raise Exception("Invalid Message Number!")

        return self.__imap_fetch_content_type(msg_nums, self.PLAIN)