<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def make_spondaic(self, scansion: str) -> str: """ If a pentameter line has 12 syllables, then it must start with double spondees. :param scansion: a string of scansion patterns :return: a scansion pattern string starting with two spondees - - - - - - U U - U U U """

        mark_list = string_utils.mark_list(scansion)
        vals = list(scansion.replace(" ", ""))
        new_vals = self.SPONDAIC_PENTAMETER[:-1] + vals[-1]
        corrected = "".join(new_vals)
        new_line = list(" " * len(scansion))
        for idx, car in enumerate(corrected):
            new_line[mark_list[idx]] = car
        return "".join(new_line)