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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def flush_to_index(self):
 """Flush changes in our configuration file to the index"""

        assert self._smref is not None
        # should always have a file here
        assert not isinstance(self._file_or_files, BytesIO)

        sm = self._smref()
        if sm is not None:
            index = self._index
            if index is None:
                index = sm.repo.index
            # END handle index
            index.add([sm.k_modules_file], write=self._auto_write)
            sm._clear_cache()