Support nbytes attribute from NumPy

Support nbytes attribute from NumPy: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). Currently, in order to get the approximate size of a h5py dataset, you have to do something like: dset.size np.dtype(dset.dtype).itemsize Where as with NumPy arrays, you can…

The task

Currently, in order to get the approximate size of a h5py dataset, you have to do something like: ``` dset.size * np.dtype(dset.dtype).itemsize ``` Where as with NumPy arrays, you can directly access this value by: ``` arr.nbytes ``` It'd be much more convenient if this could be wrapped into `h5py`'s datasets as…

Part of FineEnvs/MiMo-V2.6-RL-harbor-code.