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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 unwrap(self, dt):
 """ Get the cached value. Returns ------- value : object The cached value. Raises ------ Expired Raised when `dt` is greater than self.expires. """

        expires = self._expires
        if expires is AlwaysExpired or expires < dt:
            raise Expired(self._expires)
        return self._value