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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 literalize(self):
 """ Return an expression where NOTs are only occurring as literals. Applied recursively to subexpressions. """

        if self.isliteral:
            return self
        args = tuple(arg.literalize() for arg in self.args)
        if all(arg is self.args[i] for i, arg in enumerate(args)):
            return self

        return self.__class__(*args)