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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 _dump_csv(self, rows):
 """Take a list of dicts and return it as a CSV value. The .. versionchanged:: 4.0.0 :param list rows: A list of lists to return as a CSV :rtype: str """

        self.logger.debug('Writing %r', rows)
        csv = self._maybe_import('csv')
        buff = io.StringIO() if _PYTHON3 else io.BytesIO()
        writer = csv.DictWriter(
            buff,
            sorted(set([k for r in rows for k in r.keys()])),
            dialect='excel')
        writer.writeheader()
        writer.writerows(rows)
        value = buff.getvalue()
        buff.close()
        return value