parallel searching in multi-gpu setting using faiss
While I notice that  `add_faiss_index` has supported assigning multiple GPUs, I am still confused about how it works. 

Does the `search-batch` function automatically parallelizes the input queries to different gpus?https://github.com/huggingface/datasets/blob/d76599bdd4d186b2e7c4f468b05766016055a0a5/src/datasets/search.py#L360