Parallelizing on the CPU

Is it possible or has anyone tried to parallelize face-alignment on the CPU? I tried to do so with `from multiprocessing import Pool`, but I ran into [this pytorch issue](https://github.com/pytorch/pytorch/issues/18106).

I'm assuming the thing to do is to just run on a GPU, but I thought I would put it out there in case someone already knows a way to make multiprocessing work.

Look at the face-alignment library's inference code to understand the model loading and prediction flow. Investigate the PyTorch multiprocessing issue linked, and explore alternatives like threading, joblib, or using PyTorch's own DataLoader with num_workers. Check if there are existing examples of CPU parallelization in similar PyTorch-based vision libraries.

索引モデルが issue の本文から書いたものです。