ImportError: cannot import name 'is_fx_tracing' from 'torch.fx._symbolic_trace'

Error while running the Official Detectron2 Demo:
yesterday I ran it and it was working fine. Today, it is giving me error. Run code cell # 3 from the top. Where importing libraries. It gives error after the comment
`# import some common detectron2 utilities`
Link to the Cell:
https://colab.research.google.com/drive/16jcaJoc6bCFAQ96jDe2HwtXj7BMD_-m5#scrollTo=ZyAvNCJMmvFF
It gives error on running the following line
`from detectron2 import model_zoo`
but if you comment above line, it gives same error on next line i.e.,
`from detectron2.engine import DefaultPredictor`

Error is
`ImportError: cannot import name 'is_fx_tracing' from 'torch.fx._symbolic_trace' (/usr/local/lib/python3.7/dist-packages/torch/fx/_symbolic_trace.py)`

it is easily reproduceable as it is given by default notebook. Opened a fresh one from the link given on following page
https://github.com/facebookresearch/detectron2
Still the same error.
Someone maybe pushed something in last 24 hours that made it give this error.