docs: def process(self, tup):
          """Process steps:
  
          1. Stream third positional value from input into Kafka topic.
          """
          status_seq = self.iter_using_shelf(tup.values[2], self.tweet_shelf)
          # This could be more efficient by passing the result from twitter
          # straight through to the producer, instead of deserializing and
          # reserializing json.
          self.producer.produce(json.dumps(status) for status in status_seq)