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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 data_sessions(self):
 """ Access the data_sessions :returns: twilio.rest.wireless.v1.sim.data_session.DataSessionList :rtype: twilio.rest.wireless.v1.sim.data_session.DataSessionList """

        if self._data_sessions is None:
            self._data_sessions = DataSessionList(self._version, sim_sid=self._solution['sid'], )
        return self._data_sessions