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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 callback_result(self):
 """Blocking until the task finish and return the callback_result.until"""

        if self._state == self._PENDING:
            self._loop.run_until_complete(self)
        if self._callbacks:
            result = self._callback_result
        else:
            result = self.result()
        return result