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

        >>> print(PentameterScanner().make_spondaic("U  U  U  U  U  U  U  U  U  U  U  U"))
        -  -  -  -  -  -  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)
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

        >>> print(PentameterScanner().make_spondaic("U  U  U  U  U  U  U  U  U  U  U  U"))
        -  -  -  -  -  -  U  U  -  U  U  U