code: def _agent_registration(self):
          
          for attempts in range(MAX_REGISTRATION_ATTEMPTS):
              context = bc.context.get_admin_context_without_session()
              self.send_agent_report(self.agent_state, context)
              try:
                  res = self.devmgr_rpc.register_for_duty(context)
              except Exception:
                  res = False
                  LOG.warning("[Agent registration] Rpc exception. Neutron "
                              "may not be available or busy. Retrying "
                              "in %0.2f seconds ", REGISTRATION_RETRY_DELAY)
              if res is True:
                  LOG.info("[Agent registration] Agent successfully registered")
                  return
              elif res is False:
                  LOG.warning("[Agent registration] Neutron server said "
                              "that device manager was not ready. Retrying "
                              "in %0.2f seconds ", REGISTRATION_RETRY_DELAY)
                  time.sleep(REGISTRATION_RETRY_DELAY)
              elif res is None:
                  LOG.error("[Agent registration] Neutron server said that "
                            "no device manager was found. Cannot continue. "
                            "Exiting!")
                  raise SystemExit(_("Cfg Agent exiting"))
          LOG.error("[Agent registration] %d unsuccessful registration "
                    "attempts. Exiting!", MAX_REGISTRATION_ATTEMPTS)
          raise SystemExit(_("Cfg Agent exiting"))
docs: Register this agent with the server.
  
          This method registers the cfg agent with the neutron server so hosting
          devices can be assigned to it. In case the server is not ready to
          accept registration (it sends a False) then we retry registration
          for `MAX_REGISTRATION_ATTEMPTS` with a delay of
          `REGISTRATION_RETRY_DELAY`. If there is no server response or a
          failure to register after the required number of attempts,
          the agent stops itself.