<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 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