Download Attachments from gmail using Gmail API

I am using Gmail API to access my gmail data and google python api client.

According to documentation to get the message attachment they gave one sample for python

https://developers.google.com/gmail/api/v1/reference/users/messages/attachments/get

but the same code i tried then i am getting error:

AttributeError: 'Resource' object has no attribute 'user'

line where i am getting error:

message = service.user().messages().get(userId=user_id, id=msg_id).execute()

So i tried users() by replacing user()

message = service.users().messages().get(userId=user_id, id=msg_id).execute()

but i am not getting part['body']['data'] in for part in message['payload']['parts']