code: def _parse_authorization(cls, response, uri=None):
          
          links = _parse_header_links(response)
          try:
              new_cert_uri = links[u'next'][u'url']
          except KeyError:
              raise errors.ClientError('"next" link missing')
          return (
              response.json()
              .addCallback(
                  lambda body: messages.AuthorizationResource(
                      body=messages.Authorization.from_json(body),
                      uri=cls._maybe_location(response, uri=uri),
                      new_cert_uri=new_cert_uri))
              )
docs: Parse an authorization resource.