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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 result(self):
 """Return the context result object pulled from the persistence_engine if it has been set. """

        if not self._result:
            if not self._persistence_engine:
                return None

            self._result = self._persistence_engine.get_context_result(self)

        return self._result