Copy models back to CPU before merging them after evaluation.
# What does this PR do?
During evaluation, move the predictions from the `eval_accumulation_steps` to CPU before merging them to avoid an out-of-memory error.
_The documentation is not available anymore as the PR was closed or merged._<|||||>Thanks for your PR. This is done by the function `nested_numpify` on the line just below.<|||||>I see... I still have a problem when evaluating my model (out-of-memory). I will open an issue about it.

I'm closing this pull request, thanks!