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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 _store(self, message_key: str, result: Result, ttl: int) -> None: # pragma: no cover """Store a result in the backend. Subclasses may implement this method if they want to use the default implementation of set_result. """

        raise NotImplementedError("%(classname)r does not implement _store()" % {
            "classname": type(self).__name__,
        })