text: """
      1. 打印北京的第一个景区
         打印四川的第二个美食
      2. 所有城市 (一行一个)
      3. 北京所有美食(一行一个)
      4. 打印所有城市的所有美食(一行一个)
  """
  dict_travel_info = {
      "北京": {
          "景区": ["长城", "故宫"],
          "美食": ["烤鸭", "豆汁焦圈", "炸酱面"]
      },
      "四川": {
          "景区": ["九寨沟", "峨眉山"],
          "美食": ["火锅", "兔头"]
      }
  }
  print(dict_travel_info["北京"]["景区"][0])
  print(dict_travel_info["四川"]["美食"][1])
  
  for key in dict_travel_info:
      print(key)
  
  for item in dict_travel_info["北京"]["美食"]:
      print(item)
  
  for value in dict_travel_info.values():
      for item in value["美食"]:
          print(item)
  