如何获取json对象中的父id列表

import json

def get_parent_ids(json_obj, parent_ids=[]):
    if isinstance(json_obj, dict):
        if 'parent_id' in json_obj:
            parent_ids.append(json_obj['parent_id'])
        for value in json_obj.values():
            get_parent_ids(value, parent_ids)
    elif isinstance(json_obj, list):
        for item in json_obj:
            get_parent_ids(item, parent_ids)
    return parent_ids

# 示例JSON对象
json_str = '''
{
  "id": 1,
  "name": "A",
  "parent_id": null,
  "children": [
    {
      "id": 2,
      "name": "B",
      "parent_id": 1,
      "children": [
        {
          "id": 3,
          "name": "C",
          "parent_id": 2
        },
        {
          "id": 4,
          "name": "D",
          "parent_id": 2
        }
      ]
    },
    {
      "id": 5,
      "name": "E",
      "parent_id": 1
    }
  ]
}
'''

# 解析JSON字符串
json_obj = json.loads(json_str)

# 获取父id列表
parent_ids = get_parent_ids(json_obj)
print(parent_ids)