add shepherd requirement to an existing service?

[Remco van 't Veer]

Hi,

I'd like to add a shepherd requirement to an existing service, as
provided by guix, to prevent it from starting before some other service
starts.

For exampple: I have NAS which is very slow to start after a power
failure so I created a simple service to keep trying to mount an NFS
share until it succeeds.  This share contains files shared through
syncthing, so I want syncthing to start after the NFS service is
started.

Is there any way to do this apart from defining my own
syncthing-shepherd-service which includes the extra shepherd
requirement?

Kind regards,
Remco