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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 smart_object(self):
 """ Associated smart object. :return: :py:class:`~psd_tools.api.smart_object.SmartObject`. """

        if not hasattr(self, '_smart_object'):
            self._smart_object = SmartObject(self)
        return self._smart_object