def lbs(prefix, length):
    """
    prefix is any word you want to start a reversed enumerated sequence of labels:
        ex. lbs('in', 4) => ['in3', 'in2', 'in1', 'in0']
    prefix='@' and length <= 26 will return an alphabetical sequence of letters:
        ex. lbs('@', 4) => ['a', 'b', 'c', 'd']
    if you want to use '@' as a prefix, use '\@':
        ex. lbs('\@', 4) => ['@3', '@2', '@1', '@0']
    """
    if prefix == '@' and length < 27:
        return list(f"{chr(97 + i)}" for i in range(length))
    else:
        if prefix == '@': prefix = 'in'
        elif prefix == '\@': prefix = '@'
        return list(f"{prefix}{i}" for i in reversed(range(length)))