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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 evaluate_unop(self, operation, right, **kwargs):
 """ Evaluate given unary operation with given operand. """

        if not operation in self.unops:
            raise ValueError("Invalid unary operation '{}'".format(operation))
        if right is None:
            return None
        return self.unops[operation](right)