docs: def initialize(self, conf, ctx):
          """Initialization steps:
  
          1. Connect to Kafka.
          2. Prepare Kafka producer for `tweet` topic.
          3. Prepare to track tweets published to topic, to avoid redundant data.
          """
          config = get_config()['ResultTopicBolt']
          kafka_class = import_name(config['kafka_class'])
          self.client = kafka_class(**config['kafka_init'])
          self.topic = self.client.topics[config['topic']]
          self.producer = self.topic.get_producer()
  
          # Use own default index value while still allowing user config.
          self.tweet_shelf = shelf_from_config(config, index='pre_kafka_shelf')