code: def construct_channel(self, *args, **kwargs):
          
          channel = self.get_channel(*args, **kwargs)  # creates ChannelNode from data in self.channel_info
          city_topic = TopicNode(source_id="List_of_largest_cities", title="Cities!")
          channel.add_child(city_topic)
          add_subpages_from_wikipedia_list(city_topic, "https://en.wikipedia.org/wiki/List_of_largest_cities")
  
          return channel
docs: Create ChannelNode and build topic tree.