格式如下：
pip install -i https://pypi.tuna.tsinghua.edu.cn/simple opencv-python==3.4.2.17
pip install -i https://pypi.tuna.tsinghua.edu.cn/simple SimpleITK
pip install -i https://pypi.tuna.tsinghua.edu.cn/simple pydicom
格式如下：
pip install -i https://pypi.tuna.tsinghua.edu.cn/simple opencv-python==3.4.2.17
pip install -i https://pypi.tuna.tsinghua.edu.cn/simple SimpleITK
pip install -i https://pypi.tuna.tsinghua.edu.cn/simple pydicom