About  batch_num

Hi Thomas! 

I would like to ask how `batch_num` controls the number of samples in each batch. In theory, this should be what `bsz` should do. Taking `datasets/SemanticKitti.py` as an example, I did not see how `batch_num` is used to control the number of samples in the SemanticKittiSampler function. Is it done in training_Sampler.calibration