label_id_one = 'INBOX'
label_id_two = 'UNREAD'
# Getting all the unread messages from Inbox
unread_msgs = GMAIL.users().messages().list(userId='me', labelIds=[label_id_one, label_id_two]).execute()

{
 "emailAddress": "me@gmail.com",
 "messagesTotal": 66617,
 "threadsTotal": 14010,
 "historyId": "4618566"
}