GitLab

* [Fix]: fix label type bug when using dbsampler

* Unify cat_id for more general usage

* fix CI bugs

* keep astype np.long

* Add bottom2gravity and balance_class option.

* Add valid_flag.

* Add use_valid_flag.

* Change balance_class option.

* Add wrapper, remove gravity and balance_class option.

* Change flag, change load_infos to repeat_indices.

* Remove pdb, change docstring.

* Change name, remove unnecessary args.

* Remove _concat_dataset.

* Change name of ClassSampledDataset.

* Change docstring.

* Add get_cat_ids in nus_dataset, add unittest for wrapper.

* Change to len(self.dataset)

* Update nus data.

Update mmdet3d/core/bbox/structures/base_box3d.py, mmdet3d/core/bbox/structures/lidar_box3d.py, mmdet3d/core/post_processing/box3d_nms.py files

Update mmdet3d/datasets/scannet_dataset.py, mmdet3d/datasets/kitti_dataset.py, mmdet3d/datasets/sunrgbd_dataset.py, mmdet3d/datasets/nuscenes_dataset.py files