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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 get_campaign(self, campaign_id):
 """Get existing update campaign. :param str campaign_id: Campaign ID to retrieve (Required) :return: Update campaign object matching provided ID :rtype: Campaign """

        api = self._get_api(update_service.DefaultApi)
        return Campaign(api.update_campaign_retrieve(campaign_id))