x509 cetificate validation

Okta requires now to validate the SAML 2.0 request/response with x509 public certificate
that they providing. what should I add to the settings? I found this guide:
https://medium.com/@gohberg/okta-authentication-using-saml-simplified-python-version-74ea9d5b4be7 
but it only refers to pysaml 3 ... 
can someone help, please? 