install pytorch in code example

Example 1: pytorch install

pip install torch==1.8.1+cu102 torchvision==0.9.1+cu102 torchaudio===0.8.1 -f https://download.pytorch.org/whl/torch_stable.html

Example 2: install pytorch for windows

conda install pytorch torchvision torchaudio cudatoolkit=10.2 -c pytorch