我遇到的烧瓶SQLAlchemy的一个问题，我可以设置对象的属性place_collections，但是当我想设置为对象属性的地方，发生了错误：
Traceback (most recent call last):
File "/Users/user/PycharmProjects/website/venv/lib/python3.6/site-packages/flask/app.py", line 2309, in __call__
return self.wsgi_app(environ, start_response)
File "/Users/user/PycharmProjects/website/venv/lib/python3.6/site-packages/werkzeug/contrib/fixers.py", line 152, in __call__
return self.app(environ, start_response)
File "/Users/user/PycharmProjects/website/venv/lib/python3.6/site-packages/flask/app.py", line 2295, in wsgi_app
response = self.handle_exception(e)
File "/Users/user/PycharmProjects/website/venv/lib/python3.6/site-packages/flask/app.py", line 1741, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Users/user/PycharmProjects/website/venv/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
raise value
File "/Users/user/PycharmProjects/website/venv/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
response = self.full_dispatch_request()
File "/Users/user/PycharmProjects/website/venv/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/user/PycharmProjects/website/venv/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
reraise(exc_type, exc_value, …