如何用Python遍历N级JSON并生成树状结构？

import json

json_str = '''
{
  "id": "series",
  "css": "wrapper",
  "html": [
    { "id": "series", "css": "header", "html": "..." }
    # ...
  ]
}
'''

json_obj = json.loads(json_str)

def print_json_tree(json_obj, indent=0):
    if isinstance(json_obj, dict):
        for key, value in json_obj.items():
            print('-' * indent + str(key))
            print_json_tree(value, indent+2)
    elif isinstance(json_obj, list):
        for item in json_obj:
            print_json_tree(item, indent+2)
    else:
        print('-' * indent + str(json_obj))

- id
- css
- html
  - id
  - css
    - topbar
    - mask
    - layer
  - id
  - css
  - html
    - id
    - css
    - html
      - pic
      - total
      - news1
      - new2
      - ad1
      - list
      - pic
      - video
      - ad2
  - id
  - css
    - ad3
    - love
    - brand
    - type
- position
  - return_top
  - side_nav
- footer
  - nav