Add a new template for formatting

I am using swarm to run the services/containers. So some text is prepended and appended to the actual container name.
of this sort stackname_containername.1.pmybkzo8ovlirri0rf1syyo4p
When I do a docker stats with --format option

docker stats --no-stream --format '{{.Name}}\t:\t{{.CPUPerc}}'

It prints -

<stackname>_<container-name>.1.<some-gibberish> 0.3% ...

I want to trim the gibberish on basis of regex. These are the valid templates provided -
https://github.com/docker/cli/blob/a32cd16160f1b41c1c4ae7bee4dac929d1484e59/templates/templates.go

so I tried to use split, and was able to remove the first for 'most' containers which were same. I can't try truncate as each container names differs and I can't calculate the length. I tried pipe and then split again but since the split returned []string, it didn't work.

Is there a way to get my outcome. Should I send a PR with a new template/formatter for such usecase? Is it even a valid usecase for people?

Start with templates/templates.go and the existing docker stats --format templates. Determine whether the requested regex-based name transformation fits the current template or formatter behavior; the issue does not identify a target implementation file, test, or concrete completion criterion.