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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 sync(self):
 """Sync the write buffer with the cache files and clear the buffer. If the :class:`FileCache` object was opened with the optional ``'s'`` *flag* argument, then calling :meth:`sync` will do nothing. """

        if self._sync:
            return  # opened in sync mode, so skip the manual sync
        self._sync = True
        for ekey in self._buffer:
            filename = self._key_to_filename(ekey)
            self._write_to_file(filename, self._buffer[ekey])
        self._buffer.clear()
        self._sync = False