Submodules disappears when checking out a revision

[kerby82]

I have a git project that has several submodules, if I checkout a specific version:

repo.checkout("origin/#{branch_name}", {strategy: :force})

the submodules folder is empty and it seems I can't checkout the submodules in any way.

I see that checkout should have an option Recursively checkout submodules with same options (NOT IMPLEMENTED).

but it is not working because it is not implemented. Anyway I can checkout also the submodules through the Rugged Library?