code: def _parse_topic(client, command, actor, args):
      
      channel, _, topic = args.partition(" :")
      channel = client.server.get_channel(channel)
      channel.topic = topic or None
      if actor:
          actor = User(actor)
      client.dispatch_event("TOPIC", actor, channel, topic)
docs: Parse a TOPIC and update channel state, then dispatch a TOPIC event.