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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 value(self) -> Union[bool, None]: """Returns the concrete value of this bool if concrete, otherwise None. :return: Concrete value or None """

        self.simplify()
        if self.is_true:
            return True
        elif self.is_false:
            return False
        else:
            return None