code: def get_authn_contexts(self):
          
          authn_context_nodes = self.__query_assertion('/saml:AuthnStatement/saml:AuthnContext/saml:AuthnContextClassRef')
          return [OneLogin_Saml2_XML.element_text(node) for node in authn_context_nodes]
docs: Gets the authentication contexts
  
          :returns: The authentication classes for the SAML Response
          :rtype: list