def is_int_with_prefix(msg):
    """
    Method used check whether the given message is of format 'integer_prefix'.'integer_value'

    :param msg: message to validate
    :return: msg or raises an exception is a message is of wrong format
    """
    try:
        parts = msg.split(".")
        if len(parts) != 2:
            raise Exception("Unexpected message format. Message should be of format: integer "
                            "prefix dot integer value. Message: %s" % (msg))
        int(parts[0])
        int(parts[1])
        return msg
    except ValueError:
        raise Exception("Unexpected message format. Message should be of format: integer "
                        "prefix dot integer value, but one of the two parts (before or after dot) "
                        "are not integers. Message: %s" % (msg))