Python: if condition simplify

If it is possible to simplify if condition code in python.

download_mis = MisFromSite(id)

check_success = download_mis.getModelObject()

if check_success is None:
    check_success = download_mis.loginSite()
    login_success = check_success

if check_success is None:
    check_success = download_mis.getMis()

if check_success is None:
    check_success = download_mis.convertOurformat()

if check_success is None:
    check_success = download_mis.saveModelObject()

if login_success is None:
    check_success = download_mis.terminateLogin()

I write a code to fetch data from the website. I am unable to fetch data without login. without data, I could not process the data. each and every function is relay previous function output.