code: def confirm_not_old_proxy(loaded_cert):
      
      # Examine the last CommonName to see if it looks like an old proxy.
      last_cn = loaded_cert.subject.get_attributes_for_oid(x509.oid.NameOID.COMMON_NAME)[
          -1
      ]
      # if the last CN is 'proxy' or 'limited proxy' we are in an old proxy
      if last_cn.value in ("proxy", "limited proxy"):
          raise ValueError(
              "Proxy certificate is in an outdated format " "that is no longer supported"
          )
docs: Given a cryptography object for the issuer cert, checks if the cert is
      an "old proxy" and raise an error if so.