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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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]