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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 add_ok_action(self, action_arn=None):
 """ Adds an ok action, represented as an SNS topic, to this alarm. What to do when the ok state is reached. :type action_arn: str :param action_arn: SNS topics to which notification should be sent if the alarm goes to state INSUFFICIENT_DATA. """

        if not action_arn:
            return
        self.actions_enabled = 'true'
        self.ok_actions.append(action_arn)