Basically migrate and update `systems_to_torch` [1] since it is also part of `featomic` [2]. [1]: https://github.com/metatensor/metatomic/blob/main/python/metatomic_torch/metatomic/torch/systems_to_torch.py [2]: https://github.com/metatensor/featomic/blob/a9d358c9b4f6ddc21641dc129256e92686ca2d4b/python/featomic_torch/featomic/torch/system.py#L10-L88
