code: def is_subsequence(short_seq, 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
docs: Is short_seq a subsequence of long_seq.