docs: def _get_cn_cert():
      """Get the public TLS/SSL X.509 certificate from the root CN of the DataONE
      environment. The certificate is used for validating the signature of the JWTs.
  
      If certificate retrieval fails, a new attempt to retrieve the certificate
      is performed after the cache expires (settings.CACHES.default.TIMEOUT).
  
      If successful, returns a cryptography.Certificate().
  
      """
      try:
          cert_obj = django.core.cache.cache.cn_cert_obj
          d1_common.cert.x509.log_cert_info(
              logging.debug, 'Using cached CN cert for JWT validation', cert_obj
          )
          return cert_obj
      except AttributeError:
          cn_cert_obj = _download_and_decode_cn_cert()
          django.core.cache.cache.cn_cert_obj = cn_cert_obj
          return cn_cert_obj