def is_subsequence(short_seq, long_seq):
    """Is short_seq a subsequence of long_seq."""
    if not short_seq:
        return True
    pos = 0
    for x in long_seq:
        if pos == len(short_seq):
            return True
        if short_seq[pos] == x:
            pos += 1
    if pos == len(short_seq):
        return True
    return False
