[Feature Request] Selective Dynamics not supported in DPGEN

### Summary

Selective Dynamics option in vasp not working in DPGEN

### Detailed Description

Hi All,

I am calculating MLFF for Au substrates. Here, I optimized the Au substrate using VASP by fixing the bottom layers of Au. But when I do DPGEN to generate data, I cannot use the Selective Dynamics from VASP. Will this affect my MLFF? If so, is there any way to fix the layer in DPGEN or DeepMD?

### Further Information, Files, and Links

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