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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_deploy_key(self, auth, username, repo_name, key_id):
 """ Get a deploy key for the specified repo. :param auth.Authentication auth: authentication object :param str username: username of owner of repository :param str repo_name: the name of the repo :param int key_id: the id of the key :return: the deploy key :rtype: GogsRepo.DeployKey :raises NetworkFailure: if there is an error communicating with the server :raises ApiFailure: if the request cannot be serviced """

        response = self.get("/repos/{u}/{r}/keys/{k}".format(u=username, r=repo_name, k=key_id), auth=auth)
        return GogsRepo.DeployKey.from_json(response.json())