Gets the authentication contexts

        :returns: The authentication classes for the SAML Response
        :rtype: list

def get_authn_contexts(self):
        """
        Gets the authentication contexts

        :returns: The authentication classes for the SAML Response
        :rtype: list
        """
        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]