code: def create_async_sns_topic(self, lambda_name, lambda_arn):
          
          topic_name = get_topic_name(lambda_name)
          # Create SNS topic
          topic_arn = self.sns_client.create_topic(
              Name=topic_name)['TopicArn']
          # Create subscription
          self.sns_client.subscribe(
              TopicArn=topic_arn,
              Protocol='lambda',
              Endpoint=lambda_arn
          )
          # Add Lambda permission for SNS to invoke function
          self.create_event_permission(
              lambda_name=lambda_name,
              principal='sns.amazonaws.com',
              source_arn=topic_arn
          )
          # Add rule for SNS topic as a event source
          add_event_source(
              event_source={
                  "arn": topic_arn,
                  "events": ["sns:Publish"]
              },
              lambda_arn=lambda_arn,
              target_function="zappa.asynchronous.route_task",
              boto_session=self.boto_session
          )
          return topic_arn
docs: Create the SNS-based async topic.