<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def all_unambiguous(sequence_str):
 """ All unambiguous versions of sequence_str """

    result = [[]]
    for c in sequence_str:
        result = [i + [a] for i in result for a in _AMBIGUOUS_MAP.get(c, c)]
    return [''.join(i) for i in result]