ImportError: cannot import name '_mask' from 'pycocotools'

[CY-GAO222]

Traceback (most recent call last):
File "trainval_net.py", line 32, in
from roi_data_layer.roidb import combined_roidb
File "/data2/gcy/pruning/LTH-ObjectRecognition-main/prune_voc/lib/roi_data_layer/roidb.py", line 9, in
from datasets.factory import get_imdb
File "/data2/gcy/pruning/LTH-ObjectRecognition-main/prune_voc/lib/datasets/factory.py", line 15, in
from datasets.coco import coco
File "/data2/gcy/pruning/LTH-ObjectRecognition-main/prune_voc/lib/datasets/coco.py", line 24, in
from pycocotools.coco import COCO
File "/data2/gcy/pruning/LTH-ObjectRecognition-main/prune_voc/lib/pycocotools/coco.py", line 60, in
from . import mask
File "/data2/gcy/pruning/LTH-ObjectRecognition-main/prune_voc/lib/pycocotools/mask.py", line 3, in
from . import _mask
ImportError: cannot import name '_mask' from 'pycocotools' (/data2/gcy/pruning/LTH-ObjectRecognition-main/prune_voc/lib/pycocotools/init.py)

Please tell me how to solve this error.