1. If you use .ckpt, .geir or .onnx file for inference, please check the details in
    https://www.mindspore.cn/tutorial/zh-CN/master/use/multi_platform_inference.html

2. When using .ckpt file for inference, you can also check the details in
   https://gitee.com/mindspore/mindspore/blob/master/model_zoo/official/cv/ssd/README.md
   The steps to perform inference using checkpoint file is the same for other models (e.g., resnet50).