from requests_ntlm import HttpNtlmAuth
from pypac import PACSession, get_pac

session = PACSession(get_pac(url='mypac.pac'))

headers = {
    'Content-Type': 'application/json;odata=verbose',
    'Accept': 'application/json;odata=verbose',
}
username = 'username'
password = 'password'
url = "https://my.sharepoint.com/path/_api/contextinfo"
request_result = session.get(url,
                             auth=HttpNtlmAuth(username, password),
                             headers=headers)
print(request_result)