csrc folders

https://github.com/facebookresearch/detectron2/tree/cbbc1ce26473cb2a5cc8f58e8ada9ae14cb41052/detectron2/layers/csrc

detectron2/detectron2/layers/csrc/

It seems that csrc folder contains cpp files.

Could you tell me that it is actually used for training and testing?

or it is just used for cpp deployment

Thanks in advance