Mock SNS publish subscribe fanout in Python

class SNSMock:
    def __init__(self):
        self.topics = {}

    def create_topic(self, name):
        if name not in self.topics:
            self.topics[name] = []
        return f"arn:aws:sns:us-east-1:123456789012:{name}"

    def subscribe(self, topic_name, endpoint):
        self.topics.setdefault(topic_name, []).append(endpoint)
        return f"subscription:{topic_name}:{endpoint}"

    def publish(self, topic_name, message):
        if topic_name not in self.topics:
            raise ValueError(f"Topic '{topic_name}' does not exist")
        for endpoint in self.topics[topic_name]:
            print(f"Delivering '{message}' to {endpoint}")


if __name__ == "__main__":
    sns = SNSMock()
    print(sns.create_topic("alerts"))
    print(sns.subscribe("alerts", "email@example.com"))
    print(sns.subscribe("alerts", "sms:+15551234567"))
    sns.publish("alerts", "Server down!")