code: def _systemd_notify_once():
          
  
          notify_socket = os.getenv('NOTIFY_SOCKET')
          if notify_socket:
              if notify_socket.startswith('@'):
                  # abstract namespace socket
                  notify_socket = '\0%s' % notify_socket[1:]
              sock = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
              with contextlib.closing(sock):
                  try:
                      sock.connect(notify_socket)
                      sock.sendall(b'READY=1')
                      del os.environ['NOTIFY_SOCKET']
                  except EnvironmentError:
                      LOG.debug("Systemd notification failed", exc_info=True)
docs: Send notification once to Systemd that service is ready.
  
          Systemd sets NOTIFY_SOCKET environment variable with the name of the
          socket listening for notifications from services.
          This method removes the NOTIFY_SOCKET environment variable to ensure
          notification is sent only once.