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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 fetch(self, task_channel=values.unset):
 """ Fetch a WorkersRealTimeStatisticsInstance :param unicode task_channel: Filter cumulative statistics by TaskChannel. :returns: Fetched WorkersRealTimeStatisticsInstance :rtype: twilio.rest.taskrouter.v1.workspace.worker.workers_real_time_statistics.WorkersRealTimeStatisticsInstance """

        params = values.of({'TaskChannel': task_channel, })

        payload = self._version.fetch(
            'GET',
            self._uri,
            params=params,
        )

        return WorkersRealTimeStatisticsInstance(
            self._version,
            payload,
            workspace_sid=self._solution['workspace_sid'],
        )