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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 _set_result(self, result):
 """ Set the result of the EventualResult, if not already set. This can only happen in the reactor thread, either as a result of Deferred firing, or as a result of ResultRegistry.stop(). So, no need for thread-safety. """

        if self._result_set.isSet():
            return
        self._value = result
        self._result_set.set()