ModuleNotFoundError: No module named 'torchgen.executorch'

Ubuntu 22.04 
python 3.11.14
torch             2.8.0+cpu
torchao           0.13.0
torchvision       0.23.0+cpu
When I tried to build executorch for T_MAN, there is a ModuleNotFoundError

<img width="849" height="144" alt="Image" src="https://github.com/user-attachments/assets/e177e99f-a84d-42b3-b820-51e379c1960d" />

How can I fix it?
thank u!