get an error "TypeError: list indices must be integers or slices, not str", when build dataset

[yinian1234567]

Hi, i follow your readme to train with OpenScene v1.1. But get an error as followed :

Traceback (most recent call last):
File "/opt/data/private/openscene/DriveEngine/tools/train.py", line 279, in
main()
File "/opt/data/private/openscene/DriveEngine/tools/train.py", line 240, in main
datasets = [build_dataset(cfg.data.train)]
File "/opt/data/private/fbocc/miniconda/envs/openscene/lib/python3.8/site-packages/mmdet3d-0.17.1-py3.8-linux-x86_64.egg/mmdet3d/datasets/builder.py", line 41, in build_dataset
dataset = build_from_cfg(cfg, DATASETS, default_args)
File "/opt/data/private/fbocc/miniconda/envs/openscene/lib/python3.8/site-packages/mmcv/utils/registry.py", line 55, in build_from_cfg
raise type(e)(f'{obj_cls.name}: {e}')
TypeError: CustomNuDataset: list indices must be integers or slices, not str

I only changed the data root in bev_tiny_occ_r50_nuplan.py:
"""
data_root = '/opt/data/private/fbocc/data/openscene/openscene_v1.1'
data = dict(
...
train=dict(
...
ann_file='/opt/data/private/fbocc/data/openscene/openscene_mini_train.pkl',...)
val=dict(
....
ann_file='/opt/data/private/fbocc/data/openscene/openscene_mini_val.pkl',...)

"""

And my dataset is as followed