name 'amp' is not defined?

[liaochuanlin]

/home/lcl/anaconda3/envs/PCRLv2/bin/python3.9 /home/lcl/PCRLv2/main.py --data path_to_processedLUNA --model pcrlv2 --b 32 --epochs 240 --lr 1e-3 --output saved_dir --n luna --d 3 --gpus 0,1 --ratio 1.0 --amp
Namespace(data='path_to_processedLUNA', model='pcrlv2', phase='pretask', b=32, epochs=240, lr=0.001, output='saved_dir', n='luna', d=3, workers=4, gpus='0,1', ratio=1.0, momentum=0.9, weight_decay=0.0001, seed=42, amp=True)
pcrlv2_luna_pretask
using the reverse_aug pretrain on luna
total train images 9968, valid images 4240
Traceback (most recent call last):
File "/home/lcl/PCRLv2/main.py", line 50, in
train_pcrlv2_3d(args, data_loader)
File "/home/lcl/PCRLv2/train_3d.py", line 53, in train_pcrlv2_3d
model, optimizer = amp.initialize(model, optimizer, opt_level='O1')
NameError: name 'amp' is not defined