파이썬 dict에서 특정 key값을 끝까지 찾아내기

response = {
    'a': 1,
    'b': 2,
    'c': {
        'd': 4,
        'message': 'found it'
     },
}

def _finditem(obj, key):
    if key in obj: return obj[key]
    for k, v in obj.items():
        if isinstance(v,dict):
            return _finditem(v, key)

print(_finditem(response, 'message')) # found it
print(_finditem(response, 'description')) # None