How to support diff mode with keeping backward compatibilities?

Hi,

I’ve currently used vyos_config module and, for CI/CD, I want to get config differences before applying.

However, vyos_config doesn’t output config diffs, even in diff mode.

For outputting diff, the module has to store dict in ‘diff’ key, and the dict must have (‘before’, ‘after’) or ‘prepared’ keys.
I made PR ( https://github.com/ansible/ansible/pull/42494 ), but vyos_config use ‘diff’ key in another way.

My PR breaks backward compatibility.

Is there any workaround for keeping backward compatibility in this situation?