Updated demo.py

[ZongxianLee]

The old version demo.py is not implemented for fpn specifically. The modified version is specifically updated for detecting objects by using fpn-trained model.

[AndrewNest]

Hello, thank you very much for your update. My environment is Python 2.7.18, CUDA 9.0.176, torch 0.4.0 torch vision 0.2.1 cudatoolkit 9.0。 It is confirmed that the CUDA version is consistent with the CUDA version of PyTorch, but running demo.py still reports an error: undefined symbol:__ cudaPopCallConfiguration。Any idea about the problem? 非常感谢您的更新。我的环境是：python 2.7.18 、cuda 9.0.176 、torch 0.4.0 torchvision 0.2.1 cudatoolkit 9.0. 确定了cuda的版本和pytorch 的cuda版本是一致的，但运行更新后的demo.py依旧报错：undefined symbol: __cudaPopCallConfiguration。有什么建议吗？谢谢！