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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 assets(self):
 """ Access the assets :returns: twilio.rest.serverless.v1.service.asset.AssetList :rtype: twilio.rest.serverless.v1.service.asset.AssetList """

        if self._assets is None:
            self._assets = AssetList(self._version, service_sid=self._solution['sid'], )
        return self._assets