def is_diff(set, i):
    """Checks if the cards all have different characteristics

    Args:
        set (2D-list): a set of three cards
        i (int): characteristic

    Returns:
        boolean: boolean
    """
    if (set[0][i] != set[1][i] and set[1][i] != set[2][i] and set[0][i] != set[2][i]):
        return True
    return False