How do you pass data to and from plugins?

[SamHasler]

I've written a command but I'd like to refactor part of the processing it does into a plugin so that there could be multiple implementations for it and users would be able to supply their own. The problem I have is that the Plugins documentation doesn't show how the plugin communicates with the rest of the command.

Perhaps there are some uses of nest-commander that have more complicated plugins but I haven't been able to find any.