Error while accessing Google Contacts Groups by API - python-2.7

Question

I want get list of all groups in my contacts. I use that code:
import gdata.gauth
import gdata.contacts.client
token = gdata.gauth.OAuth2Token(client_id = "***.apps.googleusercontent.com",
client_secret = "***",
scope = "https://www.google.com/m8/feeds/",
user_agent = "GC")
gd_client = gdata.contacts.client.ContactsClient(source = 'GCv0.1')
gd_client = token.authorize(gd_client)
gd_client.GetGroups()
But got error:
Traceback (most recent call last):
File "F:/Yandex/Sites/GoogleContacts/cli_contacts.py", line 27, in <module>
gd_client.GetGroups()
File "C:\Users\Ishayahu\27Gdata\lib\site-packages\gdata\contacts\client.py", line 218, in get_groups
return self.get_feed(uri, desired_class=desired_class, auth_token=auth_token, **kwargs)
File "C:\Users\Ishayahu\27Gdata\lib\site-packages\gdata\client.py", line 640, in get_feed
**kwargs)
File "C:\Users\Ishayahu\27Gdata\lib\site-packages\gdata\client.py", line 319, in request
RequestError)
gdata.client.RequestError: Server responded with: 400,
enter code here
I have no idea what a reason and I can't find any clue how to solve it.
UPD: It looks like I should somehow put acess_token or refresh_token into OAuth2Token, but I can't understand how
so it send headers
{'GData-Version': '3', 'Authorization': 'Bearer None', 'User-Agent': 'gdata-py/2.0.17'}
UPD2: by the way, if I test in in OAuth2Playground, it shows me a page with request access to my contacts. That script doesn't ask for it. Maybe that's the problem? How can I change it? I thought, it connect with url_redirect, but I can't uderstand, how to use it
UPD3: I was right: if I add access_token, which I get manualy from Playground, all works. But how should I get it in script?!