Related to https://github.com/official-stockfish/nnue-pytorch/pull/259 as reverting this commit avoids the error. Example repro: ```bash python3 serialize.py $nnue permuted.nnue \ --features=HalfKAv2_hm \ --ft_optimize \ --ft_optimize_data=/data/fishpack32.binpack \ --ft_optimize_count=10000 ```
