ModuleNotFoundError: No module named 'torch' when installing TRT_pose

I am trying to get started using TRT_pose, but I am stuck when trying to install plugins from setup.py, using this line in terminal: sudo python3 setup.py install --plugins. I get the error

  File "setup.py", line 2, in <module>    import torchModuleNotFoundError: No module named 'torch'

But I have already installed torch, torchvision, and torchaudio with pip3 install torch==1.9.0+cpu torchvision==0.10.0+cpu torchaudio==0.9.0 -f https://download.pytorch.org/whl/torch_stable.html, so I do not know why I am still seeing this error. I am running Ubuntu 20.4 on Virtual Machine, and have Python 3.8.5 installed on it.