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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 num_dml_affected_rows(self):
 """Return the number of DML rows affected by the job. See: https://cloud.google.com/bigquery/docs/reference/rest/v2/jobs#statistics.query.numDmlAffectedRows :rtype: int or None :returns: number of DML rows affected by the job, or None if job is not yet complete. """

        result = self._job_statistics().get("numDmlAffectedRows")
        if result is not None:
            result = int(result)
        return result