def correct_penultimate_dactyl_chain(self, scansion: str) -> str:
        """
        For pentameter the last two feet of the verse are predictable dactyls,
        and do not regularly allow substitutions.

        :param scansion: scansion line thus far
        :return: corrected line of scansion

        >>> print(PentameterScanner().correct_penultimate_dactyl_chain(
        ... "U  U  U  U  U  U  U  U  U  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(" ", ""))
        n_vals = vals[:-7] + [self.constants.DACTYL + self.constants.DACTYL] + [vals[-1]]
        corrected = "".join(n_vals)
        new_line = list(" " * len(scansion))
        for idx, car in enumerate(corrected):
            new_line[mark_list[idx]] = car
        return "".join(new_line)
For pentameter the last two feet of the verse are predictable dactyls,
        and do not regularly allow substitutions.

        :param scansion: scansion line thus far
        :return: corrected line of scansion

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